since they got pretty cheap and i have some spare time i want to buy some games. I dont play online so i need couch coop or singleplayer games.
So far i got:

fallout 3 - rly liked the game
bioshok infinite - liked the game
assasins creed 4 - liked the game
farcry 3 - got kinda bored doing the same side quests over and over again...
Fifa
skyrim - didnt play yet

i thought about buying diablo 3 for offline coop, left 4 dead 2, portal 2 and boarderlands 2

what do you think about those games and what games should i buy ?

command and conquer was pretty good

mass effect series..

If your trying to play split screen with a friend id say borderlands 2 is best bet. Buy the game of the year edition and it comes with all the dlc I think. Its a really really fun game when you play it with someone. Game is seriously a lot of fun and you won't regret buying it. There is lots to do and like 6 diff characters to mess around with.