Planetside is a great game, but you can't Lone-Wolf in it without dying terribly often. I used to play it with my brother, who would sit beside me with his laptop, and we'd pilot a tank. I'd drive and he'd shoot, hover tanks were awesome. If you have a friend or friends that are willing to play with you, then it becomes a real blast. The fights are intense and exhilerating, but it gets tiresome very wuickly when you realise you need to kill something like 1000 other players to get your next License Level. I'd say 2-months is as much time as you should spend on it.
WoW, well, you know what it is. 2-3 months also for this one
EVE is special, it's not very friendly to newbies. If you know what you're doing, i.e. read up some tips and ways to get by in this game, then go for it. If you don't feel like working to have fun in a game, then this is not for you.
City of heroes is another one of those 2 months tops games.
Tabula Rasa is WoW in the future, get WoW instead. Same with Lord of the Rings.