(Note: again, I'm not going over every horror/monster game on the Genesis and SNES...just the ones I've played)Splatterhouse 3 (Genesis)
While Splatterhouse is a series that can look forward to a rebirth during this console generation, I'll always think of it as a 16 bit series. Something about the gameplay and 'feel' of the game just won't translate well to a modern console experience, but whatever. Splatterhouse 3 is interesting because, even though your character is pretty strong, the game is still creepy and scary. The cut scenes--featuring pretty realistic looking pictures--are scary, and I've always hated the fight against the possessed teddy bear after your son is kidnapped. Perhaps the most memorable thing about Splatterhouse 3 is how difficult it is. The game operates on a time limit, so you either end up rushing through levels and dying or you keep getting bad cut scenes and outright losing because you didn't get somewhere in time. At the same time, the controls are awful and clunky. Still, Splatterhouse 3 is notable for somehow combining the beat-em-up and survival horror genres.
Super Ghouls 'n Ghosts (SNES)
Speaking of difficult games...perhaps all most people know about this series is how damn hard the games are. Unlike Splatterhouse 3, though, the difficulty never comes from bad game design or poor controls. No, it's just a tough son-of-a-bitch of a game in which you can't make mistakes. Overcoming the obstacles and perfecting the timing required to progress is oddly rewarding, albeit useless, sorta like teaching yourself to write with your feet. Anyway, despite having demonic enemies and classic horror monsters (zombies, skeletons, etc.) Super Ghouls 'n Ghosts is more cartoony than the Castlevania series. But that's ok, because it's not supposed to be scary. It's just a legendarily hard game with great looking 2D graphics and a horror theme.
Super Metroid (SNES)
Though neither a horror game nor a monster game, Super Metroid still fits into the gray area of games that correspond to both horror and monsters. This is largely because of the fairly obvious influence of the Alien franchise on the Metroid games, giving them--Super Metroid, in particular--a creepy atmosphere. There's a pervasive sense of loneliness throughout the game, and while there are no 'scares' or terrifying things, per se, Super Metroid has always felt creepy to me. Exploring an alien planet, even empowered as you are with a power suit, is a bit unnerving at times, reminding one of the scene in the first Alien where they explore the derelict ship. All Halloween business aside, Super Metroid is somewhere in my top ten games ever, and if you haven't played it yet, you really owe it to yourself to do so. It's that good.
Alien 3 (Genesis)
Speaking of Alien...I didn't know until years later, but the Genesis and SNES versions of Alien 3 are different. Both have a similar sidescrolling shooter gameplay style, but the Genesis version is primarily concerned with you rescuing prisoners before the timer runs out and chestbursters rip out of them. This led to a bizarre situation in which, the first time you played a level, you would let everyone die so you could see where they were and thus plot a fast course to get to them all on time. Stranger still, the game is a convoluted mix of Aliens and Alien 3, such that you're still on the prison planet playing as a bald Ripley, as in Alien 3, but there are a ton of aliens and you have weapons from Aliens. I never got very far in this game and if I recall correctly the mechanics were a bit off. Ah well, it's still better than...
Alien Vs. Predator (SNES)
...Alien Vs. Predator for the SNES, which ostensibly was supposed to be a port of the awesome mid 90s arcade beat-em-up by Capcom but instead was a single player only piece of shit. It wasn't anything like the arcade game at all and was just a bad all around, making the Predator into a weak and awkward pile of garbage. On a side note, I've always wondered why sometimes the Alien and Predator crossovers are called 'Alien Vs. Predator' while others are called 'Aliens Vs. Predator.' There's never any consistency and it doesn't make sense because all of the ones with the singular 'Alien' have more than one Alien in them, not to mention most of them have more than one Predator. But, whatever. The SNES game is a pale, barely perceptible shadow of the Arcade version, which you may as well pirate because it'll never see another release due to licensing issues.
Castlevania: Bloodlines (Genesis)
I think there was a rule during the 16 bit era that companies would make what were NES/mostly-thought-of-as-Nintendo-franchise games for the Genesis, but they would be really freaking hard. Contra: Hard Corps. is virtually unplayable because it's so damn difficult, while Contra III on SNES is just 'typical Contra' hard. Meawhile, Castlevania: Bloodlines is ridiculously hard while Super Castlevania IV on SNES is just 'typical Castlevania' difficult. Maybe it's got something to do with roman numerals?? Well, in any case, Bloodlines is actually a really fun sidescroller which allows you to choose between two different characters (whip-y McBelmont or spear-y McWhat'shisname) and has, for its time and native platform, some incredible graphics and animation. I have to confess that I haven't played this one for years, so maybe I'm wrong about the difficulty, but I was way better at, and more patient with, 'hard' games as a kid, so if anything it's probably gotten worse. (Note: I never played Super Castlevania IV until about two years ago, so I won't be talking about it)
Haunting Starring Polterguy (Genesis)videogames. King of the Monsters may have been a bit of a counterfeit fulfillment of my dream for a decent Godzilla game, since the monsters within are generic versions of Godzilla and his foes, but I didn't care. You can't go wrong with a game that lets you play as giant monsters who trash cities and fight other giant monsters in the process. The game even rates you based on your destruction!! King of the Monsters is a fun-if-simplistic fighting game, and the kind of thing you play and never get very far in but don't care. Oddly, most of the modern day Godzilla games (specifically, Destroy All Monsters Melee) are essentially 3D versions of the King of the Monsters series.
Haunting is a game that I wish more people had played. It's actually a pretty novel concept: you play as the titular 'Polterguy', possessing objects in a house to try to scare a family out of it. Shades of Beetlejuice, no?? This game is actually really fun and creative, since most (if not all) of the objects do something unique to scare the family. You are limited by some kind of energy meter so the game is actually a puzzle game more than anything insofar as you have to figure out the fastest and most efficient way to get rid of the family. This 'possession' concept has been used in a few games since (off the top of my head, Geist for Gamecube uses it, although in different ways) but never as well.