Superman
Superman the Movie: The greatest comic book movie of all time
Superman II (Lester/Donner Cuts): one of the greatest Superhero sequels of all-time and the Donner Cut is an interesting look into what may have been. If the two cuts were spliced together it might just make the best superhero sequel.
Superman III: A truly underrated film in the series IMO, everything involving Clark/Superman is gold and the junkyard fight is one of the most iconic scenes in movie history.
Superman IV: The Quest for Peace: Can't really defend the film, it's hokey, stupid and the FX are embarrassing. But it has a good heart and Chris Reeve is as brilliant as ever. There are some truly perfect Superman moments in the film (what other film has Superman throwing stuff into the Sun.
Supernan Returns: The movie is mixed but what us great (Opening credits, Plane sequence, elevator change, Superman saves Metropolis) is really great.
Man of Steel: There hasn't been a better modern day Superhero movie for me. This film is damn near perfect.
Behind that I'd have the Batman films, then the Spider-Man films and then the X-Men films.