I still play Asheron's Call casually and like it, especially with the new low level experience. AC is the only MMO world that feels like a real world to me, not just a bunch of different theme park zones put together. That said, I'm no fanboy; it has had (and I'm sure still has) a number of flaws. I hope that it sticks around, or that someday another MMO will come close to the experience of the AC world but with a modernized client.
I've played other games like WoW and LoTRO, and enjoyed them for different reasons (mostly the experience of group questing with friends, etc.) But they leave me feeling like I'm on some kind of guided tour. Even the class-based system feels far too rigid to me. I miss skill points. I'm not saying that AC did this perfectly either--far from it--but that doesn't mean it couldn't be done better in another game.