Going off the movie, Darkseid wouldn't be a funny Mask.
If you remember, the bad guy got The Mask for a while and it didn't make him wacky - that's not what The Mask does.
What it does do is make you what you secretly wish to be - Stanley was a Loony Toons fan, the bad guy was a gangster, and their Masked selves reflected that. So, Maskseid probably wouldn't be wacky funtimes.