THE SIMPSONS / Konami / Arcade
The Simpsons is perhaps the best beat-em-up game ever, and also a testament to how to properly handle a license. The game's art style perfectly mirrors that of the show (it was created in 1991, during the second season of the Simpsons when the art was a little more jagged than it is now), the excellent soundtrack by the Konami Kukeiha Club continually and inventively riffs on Danny Elfman's cartoon theme song (in the same way they built the Teenage Mutant Ninja Turtles soundtrack around the melody to the show's theme) and the voice clips are provided by the actual actors that do the voice work on the show.
Everyone's favorite yellow family is just strolling down the street one day when they happen to stumble into a robbery in progress. An apparently hard-up Smithers is jacking the local jeweler for their loot, and during his flight he crashes into the Simpsons, with the largest diamond of his haul flying up into the air and eventually landing in the mouth of little Maggie in place of her pacifier. Instead of attempting to extract the object, Smithers simply grabs the baby and flees the scene. The Simpsons set out in hot pursuit, but an army of evil salesmen takes to the streets to keep them from catching up with the evil Mr. Wayland Smithers.
OK, so it's totally bizarre and nonsensical, but it works as a framework in which to deliver the beat-em-up action. While the majority of the enemies that you face in this one are original characters never seen in the cartoon, nearly every major character from the show at that point makes a cameo in the background somewhere as you proceed. Even Binky the Rabbit, from Matt Groening's little-known Life in Hell comic series written during his college days, gets multiple cameos.
Each of the characters has slight differences - Marge has the greatest range of all the characters with her vacuum attack, followed by Lisa and her jump-rope whip, but Konami apparently figured nobody was going to want to play as the girls and consigned them to the corners of the cabinet (the ol' Michaelangelo/Raphael treatment, as it were). Bart and Homer, the stars of the show at that point in time, are situated in the middle and seem to have shorter range but perhaps more power (though I have yet to conclusively test that theory). The neat twist to the gameplay in this one is that two players can team up for tandem attacks, with each combination of Simpsons yielding something different, such as Bart jumping on Homer's shoulders to whack enemies in the face with his skateboard.
All of this is probably redundant information for you though, as I think this game was in literally every arcade in America (possibly the world) at one point or another. Many places still have it today (in spite of it being over 15 years old), as the Simpsons are continually popular and the game is just so solid, appealing and fun. If you're a Simpsons fan and have somehow missed this one, however, you should track it down posthaste. It's an absolute must-play.
* Gameplay Video