This all depends on how faithful we're assuming the adaptation of a given character will be. I might go so far as to say that any villain can work, if the unworkable parts are "adapted out". Maybe a follow-up question for this conversation could be, "What super villain would be the most difficult to make work in a movie"?
I'd agree that we don't need to see Mxy in a Superman movie. The only way to make him work would be to make him more serious than he should be conceptually, which would just end up being Loki.
I think Bizzarro is a tough concept to adapt unless you're willing to basically ditch everything about him except for the fact that he's a clone/copy of Superman. (Geez, Superman really has some lame villains, doesn't he?)