probably SWG... :O
i know i know.... but at release, when everything was new and undiscovered, during its 'honeymoon'...
game had the best 'living world' or 'daily routine economy' of any MMO that I've played before
and the best 'proximity community' ... a term which basically means 'sense of community' that exists not in chat channels, guild chat, etc, but purely in /say to people nearby... SWG communities at release actually existed in towns, and you would actually sort of grow attached to a town and the local players there, and actually GO TO TOWN to talk and socialize with people
the daily routine of training your skills but also hunting and gathering to build and maintain a home, visiting towns to socialize about server politics, 'news' (no googling faqs or youtube walkthrough) and actually discovering the secrets of the game naturally in-game through rumor and discussion, and in general utilize or contribute to local town economies (everything player bought and sold) or infrastructure (travel, hospitals, cantinas, etc)...
i mean, in terms of story... gotta go with KOTOR. the dark ending in particular is pretty bad ass... probably the coolest 'Sith' diorama or picture-esque screen capture of any Star Wars game... in general, game captured the general theme of 'becoming' (or re-becoming lol) a jedi better than any other Star Wars game.... what I mean by that is, Star Wars is always better when you start weak and become that 'one in a million' that just by default already being the ultimate bad ass imo... in KOTOR does that sort of 'becoming a jedi' better than any other game IMO and that is a pretty iconic theme or appeal of Star Wars mythology
but if we're talking about, overall top game, regardless of what merit its based on... KOTOR is better at being Star Wars than SWG, to be sure... but SWG at release still captured a lot of Star Wars (especially for all the players who chose to start on Tatooine and basically 'lived' in Mos Eisley or Anchorhead for the first 3-4 weeks of release), and because in retrospect it has still been one of the most unique MMOs and probably by far the best 'proximity community' and 'daily life economy' of any MMO, it's probably my favorite SW game.
pity that after 5-6 weeks, the honeymoon end, the community died and daily life became a monotonous botted grind, and the lack of content deprived into energizing life to vitalize said community or economy