I played OGame and Travian a while ago.. but I got fed up after being online every hour that I was on the computer.
Haha - Ogame definitely. I was never a great player - had to spend too much time on it. I wonder how it's going on, I think I'll lurk on the forums a bit. Anyways, it was pretty fun, met some great people.
I used to play RuneScape, but it's too time consuming and most of the training seems like chores to me now.
I play Travian endlessly, it's one of the few games, browser or otherwise, that have kept my attention for years, even though the servers eventually end and you have to start over. I'd wholeheartedly reccomend it to anyone.
other than neo i play magellanwars and billy vs snakeman, magellanwars is cool but takes up quite a bit of time and billy vs snakeman if u enjoy more of a casual experience.