10. Sonic & Knuckles - The rest of Sonic 3, and less exciting. Came too late (and at the same price) to change my mind about either title.
9. SegaSonic the Hedgehog - Weird, but fun, and hard. I love the visual style in this game.
8. Sonic CD - This game is too damn big and tedious. It mostly gets a pass due to its sublime JP/EU soundtrack.
7. Sonic the Hedgehog 3 - A disappointment for me at the time. I was surprised how short it was until the rest of the game turned up in S&K. Awesome (allegedly Michael Jackson created) tunes though.
6. Sonic Generations - More of Colours, sans abilities, but made up for it with wonderful, sickly sweet fanservice.
5. Sonic Colours - After a long spell of mediocrity, console Sonic returned with a bang. Essentially a revision of the day stages from Unleashed in terms of playstyle and features, albeit with creativity and pacing hugely cranked up. And much more of it. A franchise was saved overnight.
4. Sonic the Hedgehog 2 - Feels more setpiece-y and streamlined over the first game, but still plays amazingly, features killer visuals and music, and has a legitimately fantastic finale which the first title could not muster.
3. Sonic Lost World - Once you get past the initially awkward control scheme, a fun, beautiful, deathly hard, strangely Nintendo-centric Sonic game emerges. Felt fresh and new in the way a reinvention of Sonic should, and still does.
2. Sonic Adventure - I love this game for so many reasons. The first legit console Sonic since Chaotix, my first Dreamcast game, and my first gen 6 game is a flawed, brilliant, mad melting pot of ideas, content, bravado and style. It still blows my mind how much there is to see and do in this game. I love it and always will. Phenomenal soundtrack.
1. Sonic the Hedgehog (1991) - Sega's first attempt at usurping SMB, obviously inspired by it, and most successful at emulating it. It's a game of skill and precision more than any in the franchise. Speed feels earned, momentum management is rewarded, and it's nicely challenging throughout. Still feels the most iconic to me, too.