Sky Captain and the World of Tomorrow

I thought Sky Captain and the World of Tomorrow was not very special, so I was surprised that Roger Ebert gave it four stars. However, the following quote from Ebert's "Movie Answer Man" column dated August 22, 2004, explains it:

I consider stars to be relative to genre, not absolute; since "Spider-Man 2" was one of the best movies ever made about a comic book superhero, I gave it four stars. If stars were absolute and four stars were calibrated at the level of "The Godfather" or "Citizen Kane," there might be years without a single four-star movie.

In light of this, I would agree that Sky Captain should get 3 or 4 stars, as being a very good example of the Sci-fi genre.