Speaking to Civ IV: the problem is that it is already a "war simulator". The military component of the game is the only one with a direct feedback, immediate response mechanism. You have little direct, immediate control over your economy (except through the slider); Diplomacy provides no reliable, immediate reaction to your efforts (unless they are antagonistic); on the map itself - once the world is explored/settled - there is almost nothing that provides immediate returns that is not related to war or defense.
In any given turn, there is very little the player can do to improve his economy or his diplomatic standing.
Also, as discussed here and elsewhere, war provides the quickest path to victory.
Sid said that he changed the game from an RTS to turn-based because the RTS format made the player seem like a spectator: but in all aspects of the game except war, the player is largely passive.
I love the transition to both hexes and 1UPT - I think they will make the military aspect of the game more interesting and more reliant on long term decisions (other than "build more units"). That said, I hope in Civ 5, the player has a more active role in the economic and diplomatic aspects of the game. I hope they make the game more of an "economic/diplomatic" simulator.
