In order from best to worst:
Wii - Lacks raw power, and has lots of crappy games for it. However, Wii offers the best games of this generation and has also the most diversity. Controls are much better than conventional dual analog controllers. Free online, but a bit crippled at the moment. Best choice for local multiplayer.
PC - Has a huge library of great games. Natural fit for RTS and FPS games, as well as point and click adventures and other obscure genres. Steep hardware requirements for news games is a big problem, as a hardcore pc gamer needs to upgrade every 2 years.
360 - Very powerful console with a good games library. Online is awesome, but costs a lot of money in the long run. Genres are a bit unbalanced (too many FPS games)
PS3 - Very powerful console with a lot of potential. Free online is rock solid. Lack of good games make it hard to recommend to any serious gamer.
