I'll be doing a Top Ten series as well, because as much as I like to bitch, I like to confide in people with non vital information about what I prefer out of my preferences.
Today, we have my Top 10 favorite Sonic games, dated up to 2008, I never played Black Knight.

If I had a number 11, it would be Sonic Triple Trouble (Game Gear).

Other games that didn't make it, but came close.
in no order
Sonic the Hedgehog (Genesis)
Sonic Heroes (Gamecube, Playstation2 and Xbox)
Sonic Rush (Nintendo DS)
Sonic Advance (Game Boy Advance)
Knuckles' Chaotix (32x Genesis add-on)
Sonic CD (Sega CD Genesis add-on)

Number 10
Sonic Chaos (Game Gear and Master System)
A really addictive game of 8 Bit Sonic done right, not that I'm saying that Sonic 1 and 2 on the Master System/Game Gear were bad, but this one was far more enjoyable and still offered a pretty solid challenge, the game play wasn't bad either, it was traditional to it 8 bit predecessors, 2 acts with a boss act at the end, except here there were hidden rings that you could collect to keep you in the fight, whereas Sonic 1 and 2 the boss act supplied you with no rings at all. Tails was also playable in this game and he was just as fun as Sonic, who has a standing version of the spindash, which was never in any Genesis game for some reason, it was in each Sonic game on the Master System/Game Gear starting with this one, and was in Sonic CD, it was a great feature, although pointless compared to the spindash, the novelty of it was rewarding enough.
It was significant for it's insignificance.

Number 9
Sonic the Hedgehog 2 (Genesis/Mega Drive)
I may get some ugly faces for adding this game so low in the countdown, for this game is an all time favorite to most people who know Sonic, even those who hate him in the modern day, Sonic 2 was a good game, but it's appeal on me was not as heavy as it is on most others, story-wise, the game was pretty damn epic and served as a back story to an even more epic game, and consistency in these times are wonderful, not alot of old school games has such a deep and compelling story that spans across two/three games, of course back then the story was cut and dried for me, stop Robotnik, the end. But now, looking back, that game was pretty in depth. So why is it so low in the countdown? The gameplay, it wasn't awful or anything, but it was Sonic with a spin dash, that was it. Then there was Tails, who always either got in the way or just plain made things worse. In Boss fights, he would end up hitting the boss, making me go right through him, which in some stages was the difference between life and death. He fucked up alot in special stages, eventually preventing me from getting the Chaos Emerald. I know there is the option of choosing Sonic only, but that makes it feel empty and as if I didn't get the full experience. It a hard case of picking my poison, which is why I don't play that game as often as others.

Number 8
Sonic Adventure 2/Battle (Dreamcast and Gamecube)
This was a pretty epic game, introducing an anti hero, Shadow the Hedgehog, this was back when he was a mysterious badass with an exclusive power instead of an emo with a power that others seem to be able to use for some reason, oh and working for the government. His voice was perfectly captured as well, before Jason Griffith raped it blind along with Sonic's. Then there was Rouge, you don't have to be a furry to acknowledge that she was easy on the eyes, another character who's voice was later raped by a 4kids union voice actor, the game play was core with the Sonic Adventure series, thus it felt traditional and had more of what the first game had, except and Adventure Field/Overworld. The difficulty was pretty nice and to me at least, the soundtrack was pretty badass, for all characters, except for Rouge's stages. It was also the birth of one of the most memorable Sonic themes next to His World, Live and Learn, which even non fans know of it's badassitry. Some people acknowledge this game as Sonic 3D done right, but that is debatable amongst others people.

Number 7
Tails Adventure (Game Gear)
Believe it or not, there was a Sonic game before Chronicles that was an rpg, that would be the Game Gear masterpiece, Tails Adventure, chronologically, immediately before Sonic 2 on the Genesis, or before Tails met Sonic. His forest was attacked by evil ducks or some shit like that, and Tails tends to them with Bombs and other items that he acquires in the game, he levels up every time he finds a Chaos Emeralds, and his HP increased by 10, this game is also proof that Tails' mechanical genius was not tacked on in Sonic Adventure, for he has a little buddy robot that transforms into a submarine and is also an environment scouter, pretty handy, he (Tails) also has a workshop where you can exchange between items and submarine weapons, the game is pretty epic and cannot be completed in one sitting. It has a surprising amount of depth for an 8-bit game on a handheld console. And if you can get into it, it's a blast to play, nice boss fights, pretty interesting areas, and not a bad soundtrack. Definitely one of those games that every Sonic fan should play, but shamefully does not.

Number 6
Sonic Advance 2 (Game Boy Advance)
One of my cherished preteen/early teenager games, Sonic Advance 2 was a game that I was never in the mood not to play, I remember getting it May/June of 03 from graduation (from 8th grade) money given by my grandmother, and from there I played this game every day until my Game Boy Advance broke, which was around late July early August, I eventually got a DS and bought the game again and enjoyed it since, the game was fun, had a badass soundtrack, exhilarating gameplay, it was fantastic, there isn't all that much left to say, I loved it, more than Sonic Advance 1. 3 May have been better than 2, but 2 left a mark on my childhood that I don't want gone, it gains points for nostalgia.

Number 5
Sonic 3D Blast (Genesis and Sega Saturn)
I got this game Christmas of 96, and I was hyped out of my mind. The game was great and from there, because of such fond memories, this game is absolutely perfect to play during the Christmas season. An esoteric tradition that I do every year, again, great soundtrack, gameplay, professionally speaking, could have been better, but it doesn't ruin the experience. This game gains huge nostalgic points for being a great game given to me on frigg'n Christmas!

Number 4
Sonic Shuffle (Dreamcast)
Just about the most underrated Sonic game next to Sonic Unleashed, Sonic Shuffle was a great game, plain and simple, I never saw it as a Mario Party ripoff, as I never played a Mario Party game until the latest installment of it on the Gamecube, which I hated. Sonic Shuffle was a game that required a deep sense of strategy, as the AI is brutal, even on Easy mode, the game play is pretty epic and long to say the least, the mini games were fun, the Sonic Adventure references were cool, in my opinion and was a welcome addition to my Dreamcast collection. The soundtrack sounds just fine to an 11 year old, gameplay was solid enough to keep a person interested. I think the reason people hated this game so much was the sole reason that it was apparently Sega's answer to Mario Party, once you look past that, the game is pretty awesome, especially with 4 human players going at it.

Number 3
Sonic Adventure/DX: Directors Cut (Dreamcast and Gamecube)
Talk about a die hard fan's wet dream, being overshadowed by Mario and Sony, a new Sonic game was what we needed, and Sonic Adventure came entirely out of nowhere, like a ninja in the dead of the night, it was spectacular. I remember being a kid, around 9 or 10 years old, going to a Best Buy, then spotting a giant Sonic statue to the left, and running for it.
I then layed eyes on Sonic Adventure for the first time, it was the most mind blowing thing ever. I recall some asshole in the VG forum saying that Sonic games were never high in the graphical department, well, clearly, he was an idiot, because Sonic Adventure was the first home console game with 124 bit graphics, twice the amount of the 64. Not that graphics were/are everything, but it is in fact an asset to increasing the gameplay experience, nowadays, graphics is all stock, it doesn't do too much, but back then, when you're used to scratchy outlines and shapes and botched textures, seeing a game in crisp 3D format was amazing to say the least, Sonic Adventure left a large impression on that subject, I remember finally getting my Dreamcast, and that game, I played it forever, loved every bit of it up and down, it had so much depth and love put into it, it was a middle finger to Super Mario 64 and Crash Bandicoot, who was Sony's mascot before they scrapped him in favor of appealing to the mature audience. I loved that game and still still do love it to this day, I'll start a new file just to relive the moments again.

Number 2
Sonic Unleashed (Xbox 360, Playstation 3, Nintento Wii and Playstation 2)
Before anyone asks, I am referring to the superior versions, namely the Xbox 360 version.
This game is pure gold. For me, a person who didn't mind most 3D games was completely astonished by this game, it had some of the best graphics seen on the 360, gripping gameplay, a great soundtrack, and overall, a wonderful experience. The Werehog levels were actually fun, although paled in comparison to the Daytime stages. There was a clear amount of love put into this game, which sucks, because it was thrown to the gallows like the rest of the 3D titles. I have minor problems with the game, but they in no way alter the experience that it provides. It's a shame that other people haven't tried this game out, it's great! My friend even said after looking at the gameplay that the daytime makes the nighttime seem bearable, and I agree, although the Nighttime was fun, the Daytime should be why anyone would buy the game, it's a must play kind of game experience.
Sadly underrated, but in complete honesty, a step in the right direction for Sonic, if they used this as a based for upcoming games, got rid of the Werehog and focused on the daytime gameplay, it just could very well save Sonic's reputation. Let hope Sega doesn't botch it up.

Number 1 favorite!
Sonic 3 & Knuckles (Genesis)
Remember when I said Sonic 2 was a back story to an even more epic story, this is it.
Sonic 3 and Sonic & Knuckles, smacked into one wonderfully long epic tales of epicness that in my opinion trumps anything that the SNES could offer. If you had this game, you had bragging rights. The gameplay has been touched up from Sonic 2, more, longer stages, and other great things added in. Mind blowing Soundtrack, great songs up and down, nice graphics, great gameplay, my favorite Sonic game ever, and for good reason. I loved this game so much, that in the 5th grade, I made a comic strip series themed off of this game that spanned up to 200 comics that were at the least 5-7 pages long, rarely they were 4 or 8. No lie, I'm dead serious. I love this game so much that during the same time span I wrote two stories about 20+ pages front and back based on this game. I love this game so much, that early 9th grade I made another comic that followed the game's story much more accurately, I made 2, one for Knuckles' story, and one for Sonic and Tails, each one telling a tale of epicness. I used lined notebooks about 70 pages and I filled them up front and back, I was such a great Sonic artist that most people swore up and down that I traced.
I am not exaggerating, I love this game, it gets the vote for my favorite video game period, let alone my favorite Sonic game.

And there are my top 10 favorite Sonic games, I'll be doing more top 10s in the future, so be on the look out!