A mediocre game can become a good game with the appropriate theme. I don't think just adding in the characters is sufficient though. It also has to reproduce the humor and feel of the original. Even though the gameplay is pretty generic in this game, it still does a pretty good job making you feel like you are in the cartoon.
But yeah, if you don't care for or aren't that familiar with SpongeBob then you probably wouldn't care.
I totally agree with this, many games succeeded that way: