4) Sonic and the Secret Rings: I know a lot of gamers find this game tedious, mainly due to its controls, but, once I got past the learning curve, I grew to really like this game. I love the sense of challenge the game provides.
3) Sonic the Hedgehog 3: I love the special stages, the introduction of the elemental shields, the inclusion of Tails as a playable character (who can fly in this game), and the stages, especially Ice Cap Zone. This game is even better when it's locked on to Sonic & Knuckles!
2) Sonic Rush Adventure: A huge step up from the first Sonic Rush! I love practically everything about this game! The stages and boss fights are very creative, the action is intense, and the vehicle stages are fun and make great usage of the touch screen. I have gotten a ton of play time out of this Sonic game!
1) Sonic Adventure: This has got to be one of the most underrated video games of all time! Yes, I know that plenty of gamers loved Sonic Adventure when it came out, but take a look at this Metacritic score:
http://www.metacritic.com/game/xbox-360/sonic-adventure
How did Sonic Adventure receive a 48%? That's what the XBox version of Shadow the Hedgehog got! So many of these critics agree that Sonic Adventure hasn't stood the test of time that I can't understand how some people call it overrated!
The death glitches in Sonic Adventure are so rare that I can't even justify bashing the game for it. When I died, it was usually my fault. Seriously, I ran into stuff like this in games such as Super Mario 64, and that game is awesome! One time, The Video Game Critic spoke of his method for reviewing games, and I believe he is spot on. He said something along the lines of "Some critics do a lot of analyzing in the games they review. I use my gut." When I played Sonic Adventure, I didn't inspect areas of the game for glitches; I played the game and had a fun time!
Anyway, this is one of few 3D Sonic games that doesn't overuse the automated running segments, and I also like playing as the other characters, even Amy. I didn't enjoy Big the Cat's stages as much, but I'm not going to hate the entire game because of four stages I didn't like, especially when many critically acclaimed games have issues like this (i.e. Ocarina of Time has the Water Temple, and Resident Evil 4 has an excessive amount of QTEs, and I absolutely LOVE both of these games!)
I plan on continuing this post later. I have to go now, and I'm well aware that I spent more time addressing common criticisms aimed at Sonic Adventure than I did actually justifying its spot on this list. Until then, later folks!