darknath: The atrocity here being that the PS3 isn't your clear choice!
Yeah cause everyone loves that system...
I have all 3 the wii is the least used it's almost purely a party system, The PS3 comes next it's mostly used to watch B-Ray movies, the xbox is the most used with movies watched on it multiplatform games that I don't want on PC (action games mostly but also platformers).
The other thing you have to consider is the online/multiplayer gaming side nowadays..
Wii - you need to know peoples details for 99% of games
PS3 - You have SEN(the new name of PSN probably to get away from the bad press last year) it's free but most comments floating around complain it's missing... something... SEN+ offers free games etc for a monthly fee
Xbox - Xbox live widely regarded as THE best online service on consoles, a Gold account is required for most features