Playing Monster of Monsters, to me, is like when I finally played Mega Man 1.
Full of flaws, but the potential was through the roof, and a sequel to sand the rough edges off would be amazing. Fortunately, with Mega Man, that potential was realized. Mega Man got Mega Man 2, one of my personal favorite games of all time, and that's to say nothing for the other great sequels that came out, including the Mega Man X series.
Sadly, MoM never got a 2. All the potential in the world and instead we got a completely different game that went against what the first had done.
If they had fixed some of the issues (constant black background, less repetitive levels, having to fight Gezora, Moguera, and every other monster multiple times, an unseen time limit during boss fights, etc.) and maybe if they had added a multiplayer component and given us more "Good" monsters to choose from (I'm still bummed Rodan and Anguirus didn't make the cut), a sequel or even a full fledged series could have been amazing.