I'll probably go with Dragon's Dogma Online, because it's the only one I played for any length of time, and because it was OK for a while. Plus, Capcom were very generous with free passports and presents of gems and items and whatnot, so I never felt forced to pay to win. The payment system isn't as obnoxious as it is in some games either.
I don't exactly think it's an amazing game but I haven't payed a single other game. I suppose fallout shelter kept me interested for a week. It'll have to be that for me.