I 100% agree with your comments regarding the Blues Brothers.
A short list of films which couldn't be improved IMHO
Apocalypse Now
Duvall, Brando, Hopper, Ford, Fishburne and Sheen, directed by Francis Ford Copolla. I can't see how it could be improved upon in any way. If I could be cheeky and just pick one more it would be:
The Unforgiven. Clint has made a lot of very fine movies, both as an actor and a director, but for me it doesn't get any better than this, with fine supporting roles by Morgan Freeman, Richard Harris and a magnificent Gene Hackman.