After 15 years of playing Mario and 14 years of playing Sonic, I still can't decide. Back in the 90's, they both provided us with exceptional platform games that were completely different from one another. Mario's awesome level design and coin collecting sprees were incredibly enjoyable, whereas Sonic's "cool" appearance and sense of speed made you think you were playing something truly special. In the 2D era, it's a draw for me. I can't decide.

When both characters migrated into 3D environments, Mario took the lead in great games with superb level designs. Unfortunately, Sonic Adventure, while enjoyable, wasn't a scratch on Nintendo's Mario games, and can't hold a candle to Super Mario 64 and Super Mario Sunshine.

So, all in all, Mario wins the 3D round, and the 2D round is a draw. Overall result: Mario wins, I guess. =/