I haven't watched Superman Returns, but from what I've heard it's more of a drama film about an alien trying to blend in with society and how he can't relate to the woman he loves, or humans for that matter. If that is true, that still sounds more interesting than Superman destroying Smallville and Metropolis for an hour. It might not be the exciting Superman-film that everyone wanted, but it still sounds like an interesting idea.
After re-watching the Raimi Spider-Man trilogy recently, I must say that I stand by my opinion that Spider-Man 3 is far from as bad as people make it out to be. It has some bad scenes (any of the music/dance numbers) and it throws in a few too many storylines, but I would still say it's a good, but flawed film. If the first movie was an 8.5 out of 10 and the second a 10 out of 10, I'd still say the third was maybe a 7 or 7.5 for me.
And on the topic of third movies in franchises, I think The Dark Knight Rises gets far too much hate. I remember when it came out that a lot of people thought it was the best of the franchise, but over time it seemed like the opinions changed over to "it sucks". It doesn't have The Joker, but I would still say it is a good movie. I think if TDKR had been the second and TDK the third, I think reception would have been better. I think TDKR similar to Spider-Man 3 gets a lot of hate just for the fact that it was the third film and followed what was arguably the best film of the series, and 2 of the best critically received superhero films of all time.