The games on the Wii are incredibly fun, but they just don't appeal to me as a hardcore gamer. I'll take the 360 and PS3 lineup over the Wii any day.
My biggest gripe is that while the motion controls are fun for some games, they are incredibly annoying for others. Sometimes I just want to relax on the couch and move only my fingers. I get enough of a workout from the gym -- games are for relaxation.