Another classic series full of monsters and gore is Splatterhouse. Beating demons to a bloody pulp may not seem like a big deal these days, but back when it came out for the Sega Genesis in 1993, the game was controversial and popular.
Unfortunately, Splatterhouse 3 also released just ahead of the Sega 32X in the U.S. and the Sega Saturn, making it a game that was easily looked over. It also didn't help that the marketing behind it was lackluster and any hype it had quickly died off.
The result is that these days, new copies of Splatterhouse 3 typically go for $150-$200 on eBay.