Splatterhouse.
One of the most over-the-top beat-em-up games I have ever seen, and one of the most enjoyable games I have ever played! I've done at least six playthroughs, and that almost NEVER happens for me.
Sure the gore is completely ridiculous, the story is really messed up, and the combat could be a bit repetitive, but the game had a sort of charm and personality that you just don't see very often.
On top of all that, and it just being stupidly fun, the ending is a massive as hell cliffhanger that I would LOVE to see fleshed out.
Unfortunately, due to critics bashing the hell out of this game, with only a few legitimate reasons I might add, I don't think any company will be willing to create a sequel any time soon.