If you still need a reason to get a Wii, I have one for you: Mario Kart Wii. First of all, it has many of the tracks from previous games that you know and love (Rainbow Road anyone? Pwa pwa pwa pwaaaa pwa-pwa pwaaaaaaaa pwaaaaaaa!) only with updated graphics. This Mario Kart is better because you actually "drive" with a steering wheel that you hold in front of you. AND, you can play online with people from around the world. AND, you can play with friends simply by registering their Wii ID with your system. S, L and I used to have all-day Mario Kart matches -- that is until L got carsick and had to stop playing. You can play with up to 12 people in this version!
And another reason for you to get a Wii: Wii Fit. I promise I'll exercise if P buys me this! At least once a week :)