As a movie, it was pretty decent.
Let's be honest, no one could actually make a film based on the game itself because it's just about going through stages, jumping, dodging and saving a princess so obviously they had to come up with something else.
This film was from my time but back in the 90's I wasn't really aware of it and instead played the NES Mario games though, I'll have to say, the film itself isn't actually bad if you look at it as a 'movie' than a 'movie based on a game' type.
Moving on, I've to say I quite liked all of the cast, the special effects, comedy and overall it was a fun experience watching the movie and not once did I feel disappointed by watching it.