well it depends whether or not you want me to kick you cans all over the PSN servers! yea i said it now what cha gone do bout it?
ok seriously i think i can help. i won't have any of these games anytime soon so your safe lol.
DeUS eX:Human Revolution: depends on where your friends are. if you like playing with them then i'm sure you have more on live then PSN so i'd go with live if i were you. but it seems to have more fans on PS3.
Batman: Arkham City: well if you bought the original for PS3 cause of the joker then i'd stick with PSN, and it seems to be selling better on PS3.
Dark Souls: its bigger on PS3, and if you bought demon souls then it makes more sense to stick with PS3.
Dead Island: well its a shooter
Skyrim: PC but to me PS3 seems to be the best place for it
Dragon Age: PC but xbox live would be the better choice
Battlefield3: PC but you'll likely find more people on Xbox live
hope that helped