Yes, chaning the voice of an actor can absolutly make a movie terrible. See: Most German dubs.

Historical fun fact:

Back in Ye Olde Days, movies didn’t have sound. But it had some amazing moviestars, since it takes a LOT of skill to make a convincing character with no sound.

But then, they invented “Talkies” (as in, movies where people talk). And suddenly, people like Pola Negri, a polish actress with a VERY heavy accent had some major issues. Same for Karl Dane, who had (humorously) a heavy Danish accent. They both went from top-of-the-line, A-list actors to basically nobody. Karl Dane ended up comitting suicide over it.

Other actors, like Charlie Chaplin, just really didn’t do many Talkies, except for a few VERY famous ones, his speach in the Great Dictator is famous for a reason.

They made a whole musical about this called “Singin’ in the Rain”

As far as my opinion goes. “I can’t stan ‘em”

I don’t think a movie can be “really bad” only because of a voicing, so it also can’t be elevated to good with just a voice. There are too many other factors into what makes - or for me goes into - a good or bad or really bad movie. Even when a voicing can ruin a good or very good movie.

They do have significant influence, though. Germany has a very strong dubbing industry, but I still prefer EN original voicing. And for JP anime, I much prefer original JP voicing. It makes a big difference.

I can’t say I have seen and heard many in both forms, but only very rarely do I like/find equally good or prefer the dub. There are good ones. But in the wide industry, I find them largely sub-par.

Maybe there’s more difference between different languages and societies compared to what you were asking. But I think they go into the same theme/aspect.

Not sure if Bad->Good is possible, but the other way around certainly is.

Imagine BBC nature documentaries being voiced by Gilbert Gottfried instead of David Attenborough.