Absolutely amazing from the artistic side, a fps that actually shows you how terrible war is witouth yelling what a piece of shit you are when they make you kill innocents. You're a mercenary, a death dealer, trying to make a buck killing other people, you get screwed by nature and the ever changing politics in a civil war, and now you must survive and try to get as much money out of the conflict as you can.
With mechanics like respawning enemies in territories you try and try to clear, in practice it lacks a more interesting story, but the feeling of desolation and hurt haven't been realized in any other game as of yet.
The gun play is pretty uninteresting, the rust in the weapons is a fun gimmick but gets boring pretty fast,.
A bitch to play in modern computers, but really worth it if you get it on cheap.
If it ever gets a remaster it will probably suck

Of the few good memories I have of my father going to the arcade on the city we used to live back when I was like 6 is one I hold dearly. There, in the heat of the summer, he went and got game tokens so that we could play some games. The first thing I remember was how loud the Killer Instinct on the center of the place was, and that's when I saw it. Next to the screaming arcade, there was this comparatively small box playing this rock music and screaming. The moment I looked at it and saw all those soldiers being burned I instantly fell in love with it. The feelings I got while playing it now I can't remember, but we didn't get really far into it, because the difficulty is really hard (kind of irrelevant nowadays thanks to emulation) and it just wanted to eat your coins. When we stopped, my father was really angry after spending all that money on just a single machine, so he went outside to have a smoke while I stayed inside. Looking at the screen and seeing the demo play the only thing I could think of was "Wow, videogames are amazing!". When he came back, he rushed me to home because he realized we spent two hours playing the game, dying again and again in that first mission in the ruins. When we were going outside I asked him "Dad, why do we have to leave the arcade? The machines are still on" and he responded "Because they have to clean the ashes of the soldiers we killed". I think that moment sealed the deal for me. After that, I was hooked on Metal Slug, and even if he isn't part of my life anymore (or at least don't consider him) and even if he doesn't remember that moment, it marked me to this day.
In short words, videogames ARE amazing, and you should totally try this one at least once, and if it gets to you, the saga is just full of incredible moments