I myself is a 2-D sonic fan, for two reasons:
1.) I never really got into the 3-D games. I have a copy of Sonic Heroes that I haven't ever played. The only real 3-D sonic game's I've played are Sonic R and Sonic the Fighters, and that was only because they were on gems collection! Still, what fun.... and
2.) Sonic the Hedgehog 2 was not only the first sonic game I've ever played (and wiped the floor with my brother on in multiplayer), but it was the first game I've ever played.... ever.
Maybe if they ever make another 2-D sonic game, they need to reintroduce Debug Mode. I mean Sonic 2 was awesome by itself, with the level designs, boss fights, and tails, but then you discover the most awesome cheat code ever made, which allowed you to explore impassable areas, make an infinite amount of items, and allowed you to completely redesign the stage! Maybe debug spoiled me a little bit, but it remains the most awesome code ever. I hope they make a game with that in it.