Wii: Party system, friends/family multiplayer
Wii for party / social play (Mini games [like mario party ect.] / rpg system)
Xbox 360: Gaming system, random people multiplayer
Xbox for online play (FPS system)
PS3: Gaming system, random people/friends
PS3 for self play (FPS / RPG system)
Those are what i see the systems as, and the types of games i'm looking forward to from the systems
PS: Final Fantasy FTW!