By what standard? You can't go by IMDB, that's just a populist website who's ratings are completely skewed by the fact that it's largely driven by films that people are most likely to see versus gems like international and indie films that are given rare publicity or rarely played. If you take the usual #1 or #2 on there as Shawshank (which often switches place with the Godfather)...Shawshank was a complete failure at the box office and nobody ever watched it until years later when they started playing it on weekend afternoons on cable networks and it suddenly became a massive hit and people began to click vote a lot a imdb.com
I prefer this website:
http://www.theyshootpictures.com/index.htm
which uses 1,193 critics, reviewers, scholars, filmmakers, etc. in their reviews, books, publications, polls, etc.
The original Superman is rated #782 - The first groundbreaking major motion picture Superhero. Previous Superhero films were low-budget TV adaptations or serial plays. Superman II isn't even ranked and neither is Tim Burton's Batman. In fact, no other Superhero film is listed.
http://www.theyshootpictures.com/gf1000_ranking901-1000.htm
And you go by the list of films ranked 901-1000, I admit I haven't seen them all as there are plenty of obscure films or old classic films that are hard to come by and are rarely played, but I recgonize about 1/2 of those that I have seen and what from I've seen of Superman Returns, I can't place it anywhere in that list. The only populist films you see there like Jurassic Park #904 and Who Framed Roger Rabbit #915 and Nightmare on Elm Street #958 have their place there as being major groundbreakers in film history. The first two for technical achievement for the first major hits using integration of CG and cartoon with live action and the last for being a monument in the horror genre. I don't see Superman Returns breaking any new ground.
Think about how ridiculous this thread is for presuming that Superman Returns could even feature in this echelon of films. I'm sure even Bryan Singer would agree. By the way, The Usual Suspects is #730. Assuming that the Godfather is the best film ever is also stretching it.