I always liked Sonic, although these days I'm a bit too slow and old for Sonic games, I have the NDS Sonic game, and it's very cool - like the original megadrive versions but supercharged, damn I suck at Sonic these days though. I played a lot of Sonic 2's 2-player mode, far more entertaining than Mortal Kombat and the other typical 2-player games of the day (ToeJam and Earl, gimme a break!).
Personally I'd say my all-time favorite was Sonic Adventure on the Dreamcast, pretty insane game, but I suppose that's part of what Sonic was about, pushing the most out of the hardware, like really fast and smooth running/jumping in the first 2D games, then Sonic Adventure was way ahead of it's time on the DC, and now Sonic is all grown up and on the 360 looking great.
''Stick that in your text and scroll it!.''