I can't think of a single screen to stage adaptation where the film isn't better to some degree, and that includes some of my favorites like Promises, Promises, Mame, A Gentleman's Guide, etc.
The best ones, for me, are probably Nine, Grand Hotel, and A Little Night Music. But I wouldn't say that they're better than their source material. Perhaps as good.
Personally, I think that disliking an adaptation because it doesn't keep the dusty old pop songs from the movie score shows a lack of imagination and appreciation for new material.