Very short, but very tough.
Comix Zone is a super-metafictional beat-em-up adventure starring Sketch Turner (and his rodent sidekick Roadkill), a grungy artist who is zapped into his own comic-book and must fight the powerful mutant Mortus (a boss who sort of resembles Colonel Sanders crossed with one of his own chickens). The most innovative thing about the game is that is is set within the panels of the comic-book, with Sketch hopping from one scene to the next. Secrets and power-ups can be revealed by shredding the pages too.
I'll bet my bottom dollar that the concept and execution of this game partially inspired The Matrix. When you think about it, they do have a lot in common. But CZ is undeniably 90s in its production design and style. The game doesn't last for very long but it's very challenging. The most annoying thing about it is the fact that you only get one life for the entire game and when you hit enemies it diminishes your energy bar. Not very fair.
CZ was released right at the tail-end of the Genesis' reign, but it has still become a classic since that time. Personally, I feel that one play-though is enough. This PS3 version comes with 12 easy trophies.
Lasting Appeal B-