I'm a big fan of the stage show having seen the London production in '97 and the Broadway revival in '03. I was disappointed when I saw the movie. I agree that Lewis is miscast. He's too egocentric and is missing the charm of both Raul Julia and Banderas. Plus half of the score is left out and what's included is often truncated.
Some time later when I watched my partner's DVD, I began to appreciate the film version's cinematic qualities, the performances of the actresses, and especially "Cinema Italiano". I guess I'm in the minority, but now I see it as a flawed film with more pluses than minuses. While it's not totally successful, I think it's very watchable. It's not a disaster like Mame