Yeah I was dissappointed too. For me it seemed that 2 was twice as good as 1. Then 3 was twice as good as 2. Then there was 4, about half as good as 3.

So really only equal to 2 but better than 1. But 1 was DOS so that isnt too hard to beat
The moddability of the game really helps... sorta. If you know what you are doing which I don't.

I think threads like this are a good thing. It helps those of us who are frustrated to vent a little bit.
Wow, I'm the exact opposite. I got tired of how tedious Civ3 was with worker management, and the lack of built-in stack management. I tried to find ways to win the game quicker just so I wouldn't have to clean up pollution in the modern age (ugh...), and I avoided anything larger than a Standard map like the plague.
But in Civ4, you can stack move workers, so you can create the minimum number of workers in a stack to clean pollution, and just move the stack and click one button. Done! This was a dream come true!
Additional buildings, additional troops...if you are building every building in every city, you might want to stop. My military production cities typically have barracks, stables, and forges but rarely universities or banks (take too long). The cities now are no longer generic locations where you farm or mine around. There are several terrain improvements (although some can only be put on special resources) and buildings to allow you to customize and specialize your settlements.
One thing I miss was the modern age Nuke submarines, tactical nukes, paratroopers...they've been mentioned before, but that's what I want in the game next (please, next expansion pack...dozen civilizations, two dozen leaders, and these units!).
And the implementation of religion--I'm impressed by it. And how the great people work, and the civics...I think this is a case of being overwhelmed. The fact is, I'm trying to figure out how. The game uses a simple point-and-click interface with no goofy menus with special options or weird button combinations to do things. If you don't know what to build, it gives you recommendations while you learn. It gives you worker recommendations. It gives you places to settle, etc. Overall, I found it easy to get into Civ4, and once I stopped trying to play it like Civ3, I enjoyed it even more--less micromanaging, more features that are easy to use because of the simple methods by which they have been implemented. By the way, if you are trying to use your Civ3 strategies in Civ4, I encourage you to take a peak at an article in the War Academy.
There's my $.02. I know the critics of the game probably won't care, but this was a great step for the Civ series--less micro, implementing the good government system from Alpha Centauri (why didn't they do that in 3?), etc.