That pretty much depends on the stage. I guess most of them come pretty close to their source.
But in many cases I had to edit the sprites, since many stages didn't had the minheight of 240 px
and in other cases the parallax effect in the sourcegame was so fucked up (chars sliding), so that I did a proper version in mugen,
so not really accurate, but more an improvement.
Thanks for the comments by the way