Sony:
Like - Nostalgia factor, good controller, best exclusives
Dislike - PS3 was a bit of a disappointment hardware wise, too expensive, online not as good as XBL
Microsoft:
Like - Best online, 3rd party support
Dislike - Unreliable hardware, terrible 1st party, Kinect is super lame IMO
Nintendo:
Like - Fun, has some decent games
Dislike - Overrated first party (but still pretty good), too much motion control not enough standard controller, meagre 3rd party.