Everyone mentions AoC and TLW but how bout some Anarchy Online? shit was dope back in the day. One of the most revolutionary MMOS for its time. Mission system, random generated dungeons, chat system with bots and all sorts of creative shit you could do, and also the first to have linked items in chat. They had social dungeons that were also instanced, best of both worlds IMO. So much in that game was way ahead of its time.