I think "Mystery Men" is fantastic. It's not flawless, and I'll get into that, but as a 90's movie and a movie that came out during the bleakest time for comic book adaptations, I think this movie is an absolute gem. While the characters are pretty straight forward (one would say flat) having strong supporting role actors to portray them elevates them quite a bit. Who would've thought The Shoveler played by William H. Macy could be a loveable badass. Or The Blue Raja being aloof with a heart of gold all thanks to Hank Azaria's portrayal. Geoffrey Rush as the villain is downright perfect. And holyshit, Gregg Kinnear as Captain Amazing. This movie is a gallery of late 90's actors and comedians who got wrapped up into such a weird adaptation of an already bizarre comic, and while the low budget shows in the execution of some sequences it makes up for it with its writing. It seems there was a lot of issues behind the scenes, with the actors going at each other trying to get their own style of comedy, but as a whole the movie's comedic tone works pretty well. Hell one could argue that this tonal dissonance only adds to the theme. These are very different characters pushed to work together, and while the conflict gets resolved in the end they don't all kiss and make up at the end. Their own personal character arcs are completed, but you don't really know they'll keep working together in the future.
But speaking of not working, yeah lets talk about the set ups, because this movie kinda falls apart on the visual department. Not to say it's not visually stimulating (the CGI gets to points where it's so bad it's actually great), but almost every scene in the movie is shot in flat, bland camera angles, like a sit-com. The editing and camera work are very boring, there's no energy to any scene, and any use of interesting camera work gets lost in the mix. It's like a bowl of porridge that only has two small dried up strawberries in it. You could say this only adds to the comedy from the characters, but a movie so odd needed a different style of direction, like what they did with "Freaked" or "Dark City", something that has more personality. As it is, it feels like the director wasn't feeling it at all, and it's more a product of the studio that was saved by the actors and the relatively strong writing.
In conclusion, "Mystery Men" is an oddball from a decade that was so marred in mediocrity that the actual gems got lost in the shuffle, only to be remembered by weird guys on the internet like yours truly. With the mainstream appeal of superhero movies we should look back and see what they used to be, and how a movie starring Ben Stiller as a very angry guy was the 90's equivalent of Guardians of the Galaxy.