I think most of these are ppl who just link music to games that are nostalgic to them, not really music that are actually really well done for a game, i've yet to see anything in this thread that even comes close to the quality (and effort/cost of production) of the music in lineage 2
Gameplay wise I only like Ragnarok Online not Granado Espada. But I still love Granado Espada's OST. So it's not just liking the music because it's nostalgic. More like I really love the ambient trance music in MMORPGs.
Cant believe no one said lord of the rings online. Its the only game where I leave the background music on.
Final Fantasy XIV: A Realm Reborn, best music I've heard in a long time.
I do like the music from FFXIV:ARR. Garuda's Theme & when you're fighting Twintania is in Coils Turn 5 are my favorites.