Just the one? or do you cycle in between them whiles waiting for new content to pop up? Which is your highest priority?or do you just stick to one.
I myself I'm on about 4, possibly looking to extend 5-6 ... I get different things from different ones, but largely I just play their world, enjoy the fantasy and play which ever has content going.. I must say I do like different things about all of them. I love how GW2 and FFXIV encourage group play, I love the combat animations and effects of SWTOR and it's story presentation, I love wow's increasingly amazing diversity and very well tailored themes. Haven't had much time to get into WS or ESO, but they're next on my list, I'd probably stick to doing 2 subs - GW2 and SWTOR I can manage playing most of the time without subs, and only sub to sWTOR when they're raid content otherwise it's alts and stories. WoW and FFXIV need subs, so i'd probably keep those up, and i'll need to monitor how ESO and WS turn out to decide if i'd do anything.
anyway..
I'm a sucker for
1. Really cool lore - an interesting story, and when it's presented well /drool
2. Character creation - my toons need to look good, I stare at them all the time, the better a game's capability of designing a really nice looking too, hte more i want to play that character.
3. Animations - looking cool in combat is really important, fancy stuff, i must say SWTOR and GW2 lead the way here - soz WoW and FFXIV
4. Fun combat gameplay - I gotta have fun playing it and I usually like a fairly high degree of mastery, don't like know it in seconds classes, and i'm fully aware you can be simple but have depth, that works for me, but so does complex - GW2, WOW do this really well, but SWTOR I have had a lot of fun on too
5. Great class themes - this really helps me get into playing more, especially for repeat value when you've done the story already x number of times with various alts, what keeps me playing is class mechanics and theme - WoW & GW2 does this really well, but SWTOR and Lineage 2 are masters of this. I wish GW2 didn't give their Ranger a pet, i'd have had an excuse to play both a hunte ron wow and a ranger on GW2