Don't completely rule out online play. For things like shooters and racing games, online extends the life of a game massively. When I'm pressed for time, I can always go online for a blast of Team Fortress 2 or something for half an hour. With most games that's barely enough to finish a level.
The Wii is enourmously fun with people in the same room, but the majority of games are limited to cute sports simulators and minigame collections, which can be fustrating for more seasoned gamers. There are exceptions (Zelda and Mario) but the limitations of the Wii mean that they're never truly on par with 360 and PS3 games of a similar genre. The only excpetion to this I can think of is Mario Galaxy.
Of the PS3 and 360, I would say that the 360 has the most appealing library of games, but that is much more down to your personal taste.