I must contradict quite a few people on this discussion, my apologies for that.
First, even without expansions, this game is really good. While it maybe lacks stuff in the eyes of somebody who is used to playing with the expansion(s), I never got my hands on them, so I only know vanilla. The game has a 100% replayability value.
Second, a game does not take that long. Granted, I do only 2-player games, and both me and my fixed adversary have become quite skilled in this game, so we don't have any of those awkward moments where you seem to wait an eternity before it's your turn again. A game takes between 2 and 4 hours, but most of the time we kill the big boss around the third hour.
There is one big flaw in this game, though, and that's PvP combat. It's tedious and boring, and the only thing you get from it is a stupid item, maybe some xp and gold if there's a "Bounty" or "Old hatreds" event in play. And to be honest, ending the game with a PvP battle feels truly as a hollow victory, 'cause you know that the big boss is still roaming the countryside. It's a boss-kill, or nothing
As an endnote, I must say this : It's a true shame that this game has been discontinued by every party involved. It rules in a way like Warcraft II ruled the pc-game community back then