Metal Slug 3 is an incredibly enjoyable run'n gun game. Run to the right, blow shit up. Simple as that. Not much more to explain than that. The series just kinda didn't get better than this one.
Gameplay wise, it's a lot of fun. You run around, free and save hostages, and shoot everything that isn't a background object or is being used by yourself. Throw hand grenades, shoot with the "ROCKET LAUNCHER" and pick up the many, many powerups that will shout at you, "HEAVY MACHINE GUN". Granted, the voice shouting at you is a bit cheesy, but it does honestly add to the charm of the game.
The game has 5 levels, but also multiple pathways, usually having to do with a sub of some sort. They do add to the replayability, as they can change how you play the game. Levels 1 and 3 have them undoubtedly, and would be in places you wouldn't really expect under most circumstances. Level 5 though is a long, drawn out pain in the ass. First, your character gets abducted by aliens, then you go up to space and give chase. The mothership is not hard, it's just really, really, REALLY long. At least 20 minutes. And believe me, you will feel it. The rest of the game doesn't drag out like that, but there are a few level gimmicks that do tend to get on my nerves. Level 2 for example. Getting bitten or barfed on by a zombie, turning into a zombie, then not being able to avoid shit because I couldn't move fast enough.
Graphically, this game is very pretty. It's sharp and everything moves smoothly. As is to be expected with any MS, there is a bit of lag sometimes, but it's alway running at a smooth 60fps. The look is sharp down to the pixel. So sharp you might cut yourself on it.
Sonically, this game is good. Voice clips that are a bit cheesy, such as the staple "HEAVY MACHINE GUN!" or such add to the charm of the game. The music isn't really that memorable, but that's mostly because I wasn't paying attention to the music but instead the gameplay and making sure I focus on what is flying at me and avoiding what can be avoided. The music isn't bad. I just never really paid attention to it. The clips are a bit crunched, but you can't really complain about that.
Control wise, It's solid. It's snappy. Zero lag. Plays as it should.
There are also extra modes in the home ports, such as Mothership and Fat Island, and a level select.
Don't bother with Fat Island.
I overall did enjoy this game, and I would recommend that you play it. Only problem is that it is the type of game where you can go and ruin friendships by taking all of the powerups. Play co-op at your own risk. Also, lots of tanks, hand grenades, and HEAVY MACHINE GUNs. Not much else to say though, as the game looks good, plays good, and sounds good.
Highly recommended, all three, MVS, PS2 and Xbox versions.