I've been playing my PS3 mainly lately too. I can see where your friend is coming from.
Trauma Center, Zelda, and WarioWare: Smooth Moves only have so much replay value. You can only get try so much to get all "S" ratings in hard on Trauma Center, and can only explore the entire Zelda terrain so much. WarioWare was very short. Wii Sports is still awesome for replay value, though. I can't wait until I can get more games for the Wii that I like.
Resistance: Fall of Man on the PS3 however I've been addicted to. I've beat it on Medium, Hard, and SuperHuman (unlockable) modes. It is addicting as hell to play online! Once Wii has some online games I'll be playing it more. I LOVE playing games online.
Different demographics like different types of games. Some people prefer online multiplay, some people prefer intuitive controls. Me? I'd love to see both, and I know the Wii will provide, just not at this moment. I still love the Wii, though.