1991 was a incredible year for side-scrolling beat'em up (or hack n slash) games. My three favorite games of all time from the genre, came out in that year. Two of them, are hidden gems that most people probably never played. And one of them is The King of Dragons, in my opinion, the second best game of all time in it's genre after Turtles in Time. It has a medieval setting, that gives you five different characters from you to choose from: Dwarf, Elf, Cleric, Fighter and Wizard.
The game has a really great look and feel to it, it's an amazing couch co-op game and has a very nice upgrade system, you can find a item in crates and/or after bosses that upgrades your weapon or armor. With the number of characters it's also a great game to replay. It's the kind of game that I wish everybody gave it a shot, I'm a big fan of this type of setting as well. The King of Dragons is a hidden classic.