Lord of the Rings Online and Star Trek Online have already been mentioned a few times, so I'll just add my recomendation to them.
And to Fallen Earth, a less well known post apoc MMO with first/third person shooter style combat a huge open world to explore, in depth crafting and a mainly pvp focused endgame that's pretty active now that they've had an influx of new players with F2P.
Finally, a sort of recomendation for City of Heroes. I've had a lot of fun with it and it's the best (IMO of course) of the superhero MMOs, but I'm not overly fond of the F2P model it offers.
And to Fallen Earth, a less well known post apoc MMO with first/third person shooter style combat a huge open world to explore, in depth crafting and a mainly pvp focused endgame that's pretty active now that they've had an influx of new players with F2P.
Finally, a sort of recomendation for City of Heroes. I've had a lot of fun with it and it's the best (IMO of course) of the superhero MMOs, but I'm not overly fond of the F2P model it offers.