The Producers was really funny on stage. I laughed my ass off. :-\ It wasn't deep moving theater, but it was some classic vaudevillian spectacle. The movie was not good because they basically did the stage play for the camera, which doesn't translate AT ALL.

I also enjoyed The Full Monty and Dirty Rotten Scoundrels musicals as well. It's not an automatic recipe for failure-- you can still get great songs and performances out of adapting pre-existing material.