Xbox360 has the best price/feature ratio, there are many excellent sport games out there (Madden, etc.)
Get a PS3 if you plan to watch Blu-Rays in future, but its price isn't pretty attractive yet.
Both platforms offer good RPGs and Shooter Games.
Avoid the Wii if you are looking for real sport games. Wii Sports and Mario Striker are fun, but no sports games.
Edit: just noticed, that you already own a Wii , dooh







