When a game has an M rating, normally its for something stupid like foul language. When Splatterhouse has an M rating, its because if it doesn't bleed, swear, or look like something that should be inside of the body as opposed to where it is, then chances are its a naked photograph.
Game play wise, it's a pretty dang solid game. Classic block/dodge, light attack, heavy attack, "special" mask move, "berserk mode", and grab move buttons all exist. Most sections involve simply beating the crap out of everything in the area, then moving to the next, with some mild interactions of "pick the blood sigil that is correct or fight more bad guys" and "throw bad guys onto these spikes to unlock the way" thrown in. In a classy, nostalgia-ridden move, they have also set some stages where the view point suddenly changes to that of a side-scroller, which adds a little bit of something different that is still mostly the same to the play. Moves/skills are unlocked via earning blood/necro, which is earned by (what else) killing the faces off of anything you come across. And I mean literally killing faces...
The game incorporates 'Splatterkills', which are nothing but a gruesome and cool way of finishing off a guy who has been pummeled to the point of a red outline. These kills, outside of looking like they would hurt extremely, net you the most blood for your punch, and also sometimes net you an appendage to beat someone else with. Yeah, you can pick up severed arms and heads, then use them to beat their friends with. In some instances (these particularly annoying blue-veined ghouls), enemies will even cause you to loose an arm. This effects numerous things and is quite inconvenient (you move slower, can't grapple, can't run, can't do combo attacks, can't use weapons), although using the games healing move will automatically regrow it if you don't feel patient enough to wait for it to come back by itself. Each enemy has one or two splatter kills associated with it (from what I can gather), but the face button's required to push will randomly change (by face button, I mean your A B X Y buttons). Also, a one-liner will normally be spouted from the Mask (the Terror Mask), such as "Hey, it's a twist top!"
Graphically the game is no push-over. Violence sticks around for a while, both blood-splattered floors and walls, and on Rick (you), making him look downright frightening at times. Damage to Rick is also displayed on him, leading to visible ribs, bones sticking out from severed arms, and all the pleasantries of such carnage. The in-game collectibles (Jen's Photos) are another part of the M rating (as if the Mask's constant swearing, sexual innuendos, and violence weren't enough already), as at least half of said photographs are generally topless (and there hasn't even been a big deal about it in the news or papers yet?). Honestly, this doesn't bother me, and if anything it's more incentive to get than some little dog-tag or laptop that does nothing anyways.
On the audio front, I have to give the game my vote for "best soundtrack of the year." Why? Its practically all Metal, and I like metal. Even if you don't like metal, it belongs in a game such as this, where the heavy pounding beats and violent guitar riffs only fuel the carnage you are about to unleash on the little digital world. The sound effects themselves are good, letting you really know just how much it hurt to get hit by that lead pipe a second ago. The voice over jobs are actually rather surprising. I've played more serious games that weren't as convincing as this, even when it starts to break that 4th dimension with comments like "This is what got us an M rating kid."
The largest downside to the game is the ending battles. I mean, there is one point at the start that involves some platforming that was rather difficult, but at that point its the only platforming you've done in the game, so you are totally not ready for it. The end of the game though...it quickly turns into a series of mini-boss type enemy fights. And not just one after the other, but at one point you have 4 of one type of mini-boss and 2 of another type all at once, and your expected to deal with them. To do this normally is just plain a nuisance, so I ended up resorting to using "berserk mode" to clear majority out as quick as possible (this can be seen to an extent in the video review). Also of note, by beating story mode you unlock all three original Splatterhouse games to play, and there is also an Arena mode, which consists of beating the crap out of 20 waves of enemies to get a "rank", based on time, performance, and how many of the "hidden bonus objectives" you completed.