I have all 3 and have played video games since the old atari and intellivision systems I have had them all except for the neo geo.
Likes:
360
Great games
Live is very user friendly and is second to none
achievments add some more playability to games
Mic hooks up flawlessly and all live games support it
dislikes
I hate how they still charge points for themes that is over a year old
RROD they replace your system but it still sucks when it happens
Its loud
P!tu squeeling like a girl when you race cars on GTA4
PS3
Blu ray player
I like how you can make your own themes without paying for them
MGS4 and MGO
It is a quiet system
dislikes
PSN it might be free but lets face it....it sucks
no achievements or messaging but I hear that is going to change

Hooking up your headset and then praying that it will acually work in game
Cant invite friends to join you in the game you are playing
needs more great games
Wii
Fun games
I love how they incorporate the wii mote into the games
easy to set up and use
great party system
very easy to pack up and take with you
Trauma center great game and perfect for the wii mote
dislikes
online system just plain sucks and it refuses to connect to a dsl wireless router
needs more games that take advantage of the wii mote
I could think of more likes and dislikes for all the systems so I just listed the ones that matter to me