WoW > *
Been playing for just over a year now and I'm still not bored. With Naxxramas (new raid instance) on the way I doubt I'll be getting bored any time soon. However, private WoW servers suck. Hard. I've played a couple of successful RO servers before, they're usually fun. I'd say whatever you do, don't do Mir unless you've got something really new and innovative to attract people. I stopped playing Euro and private Mir over 4 years ago and it was boring as hell. Since then I sometimes check what's happening with Euro/private Mir and not a lot seems to have changed. A few new bosses, new mobs, new items... nothing special.