If you played Tropico 3, you've also played Tropico 4.
Turns out, Tropico 4 is exactly like its predecessor - with minor and very subtle graphical changes (mostly to the menu), hardly to be called improvements.
There are a few (literally, a few) new building and some new campaigns. That is all we've been waiting for 2 years for. The disappointment is definitely there. I don't think I've ever seen such few improvements - it hardly deserves a "4". Definitely feels more like an add-on. A downloadable add-on, may I add. It's a time-waster one way or another - if you've played Tropico 3 before, there's nothing in the 4th installment that will keep you interested. If you've never played Tropico 3 - you still want to play it, since it's a great strategy. Which brings you to square one.
Tropico 4 gets an F for effort. Or the lack of.