You got a few choices;
WoW. It's polished, you know what your gonna get and even 10 years later is still an amazing game,
Wildstar. First impressions are Decent. Levelling is a bit boring, nothing new or innovative, the end game looks interesting but can't say for sure.
Rift, i played it for 6 months or so, is free to play (at the time I played something's that I require mandatory such as AH access were needed to be purchased via it he in game cash shop). Over all was a decently fun game for a few months, raids felt lacking (coming from a top 50 WoW raiding guild), PvP was just bad and dungeons/farming were quite dull.
I hear eve online is great, not tried it but it looks fun.
I'd say get wildstar.