ALIEN VS PREDATOR / Capcom / Arcade
The "beat-em-up" as a genre largely had its fortunes tied to the arcades that it originated in. When the arcades really started dying out in earnest in the mid-90s, so did beat-em-ups.
A shame for Capcom, at least, because they were doing their best work in the genre between 1993 and 1995, right when the traditional arcade really began to start circling the drain. Alien vs Predator falls in the middle of this period, and while it's not as innovative as their non-linear Dungeons & Dragons games, it's great-looking and adds an even more robust move set.
The setup is that Aliens are swarming the fictional California city of San Drad out of nowhere, and our two space marine protagonists got themselves caught there. Fortunately, a couple of Predator bros surf in and are like "Woah the hunting is GREAT here!", so this unlikely team will fight their way out and try to solve the mystery of this sudden Alien invasion. Even though there's four total players, my research indicates the cabinets only allowed three at a time -- the one cabinet I personally saw of this game in real life back in the '90s had only two players. Anyone can select any character from any position, of course, and you can change characters when you continue on a new credit.
The game is composed of seven fairly lengthy levels. The first half has you up against a small army of Aliens, but the second half adds heavily-armed humans to the mix as you uncover the conspiratorial source of this sudden Alien immigration wave (good ol' Weyland-Yutani fuckin' up everything again, of course.) The game actually appears to have been based on the original Alien vs Predator film script, but of course that project got stuck in development hell for a decade and eventually came out as something completely different.
Aside from the great-looking graphics, which appear to have been done by the artist(s) also responsible for the Darkstalkers games, it's the unusually wide range of moves and the significant gameplay differences between each character that really make the game and set it apart from most of the '90s beat-em-up crowd. Each character has a primary melee attack, each of which combos differently and has different range and priority. For example, the diminuitive Lt. Linn makes up for her lack of beef with a longer attack combo that automatically chains into a rush and is great for cutting through crowds, while the heavy cybernetic tank Major Schaefer has kind of a crappy short-range attack with his cybernetic arm, but can swing any dropped melee weapon that he picks up rather than doing the one-time throw that the other characters do with it.
And that's just the beginning. Each character has their own unique sidearm, jumping and diving attacks, throws, air throws and a dashing special move that can be chained into from the standard attack combo. Each character also has their own unique sequences to air-juggle enemies that you can learn by experimentation.
I guess hardcore series purists might be mad that the game basically trivializes Aliens by throwing hundreds of weak, disposable ones at you. If you're not hung up on all that, though, it's kind of interesting to get the Japanese anime-styled take on the franchise. It's also an interesting look at what the original AvP movie might have been like if it had stayed on track.
As of this writing, the game has no home console or digital download port despite its general excellence, so MAME is your only option unless you've got access to a cabinet somehow. There was an AvP beat-em-up for SNES, but it's a completely different game by a completely different team.