It isn't 'campy' or 'cheesy.'
The 1967 Batman, with Adam West, is campy and cheesy. Popeye is subtle and funny. I think people who call this movie a "guilty pleasure" or worse still, hate it, just don't understand it.
As an interpretation, it has a few shortcomings. The cast is imperfect--I don't care much at all for the inarticulate Italian Bluto who makes animal sounds and has dubbed English dialogue. Shelly Duvall is almost too pretty to be Olive Oyl, and J. Wellington Wimpy, who could have been hilarious, was totally wasted in this film.
But the other elements of the movie are fantastic. The in-cast chemistry is superb. Robin Williams and Ray Walston are excellent. The musical numbers are very good and the storytelling by Robert Altman and Jules Ffeiffer lives up to both their reputations. The Sweet Haven set is wonderful and so are the minor actors and extras who populate it.
Even Disney seems to have forsaken it. I have no idea why. It's a great film.