It's controversial, but not without its benefits. Really depends on the type of gameplay you're going for, IMO. I enjoy a very diplomatic game of Civ4, for instance, and I try to squeeze every ounce of quasi-emergent diplomacy and even policy gameplay from what little I feel is there. But I realize I'm in the minority on this. Most Civ gamers seem to prefer a purely military game. In fairness to them, that's the clearest objective of the game. But I like that Civ allows you, albeit with a great deal of against-the-tide effort, to play a different type of game.
I never made the leap to Civ5, due to what I perceived as oversimplification, and a trend away from precisely those features I liked (but which everyone else seems to hate). So I can't really comment there.