The 3rd movie is probably my favorite of the 3. I was never a huge fan of the first, to be fair (though it's not bad by any means, mind you, just saying you won't see my raving about it), but whatever.
Big thing the third movie does is handle the whole idea of "Growing Up" in a kind of bitter sweet way, one that many can somewhat relate to, while not being actually emo about it, and you don't really feel bad about any of the characters in question.
It also has the only villain I know of who smells like strawberries which pretty much invalidates all negative arguments you can say about said villain!