I am a huge fan of MGS games. I was introduced to MGS series somehow late, in 2001. the first game I played is MGS - Shadow Moses Incident, I think this is the one you played. I don't want to extinguish your appetite, but in my opinon, even though it the poorest graphically, it's the best content-wise. The dialogues, camera angles... Every fox-hound member has its own story and motive, and this makes their character deeper. Video gaming at its perfection!
series went on with MGS2: Sons Of Liberty, which is far superior than MGS1 in gameplay and graphics. It is a good game, yet it becomes somewhat annoying(ly) complex towards the end. Enemy characters aren't so well designed... I don't know, I have mixed feelings toward that game.
finally, there was MGS3: Snake Eater, although launched 3-4 year later, graphics and gameplay aren't that MUCH improved as one might expect, comparig to MGS2. story is good, gameplay is the same but more detailed and enjoyable. but this time, the story has nearly no philosophical dimension. comparing it to MGS1,would be like comparing Matrix Revolutions to Matrix 1.
anyway, to play the whole trilogy is a must, to anyone!
as for bonus, there's a Metal Gear Acid series for PlayStation Portable. gameplay is so much different. it's turnbased. To me, even though it was radically different, MGA1 gave me the closest experience to MGS1. it's different lots of people hated it, but I highly recommend it.
if you liked MGS series, and have a PC, you should buy following games, they're old, thus cheap and graphicaly poorer. but they will beat any present day game in depth and gameplay. You can finish all of them without killing anyone, with your wits, your words and your sneaking abilities. None of them will disappoint you if you loved Metal Gear Solid 1. (and even surpass MGS)
Thief 1: The Dark Project http://www.gamespot.com/pc/action/thiefthedarkproject/index.html?q=thief
(Awesome game, you're a thief in a fantastic setting, and you become a part of an exciting story, unknowingly)
Thief 2: The Metal Age http://www.gamespot.com/pc/action/thief2themetalage/index.html
(sequel)
Deus Ex http://www.gamespot.com/pc/rpg/deusex/index.html
(Near future doesn't look good... diseases, controlling governments, technology serves war, disputes and riots everywhere... in the midst of all, you're a huge project: A cybernetically enhanced human being. and will have an impact on the world)
Arx Fatalis http://www.gamespot.com/pc/rpg/arxfatalis/index.html?q=arx%20fatalis
(again a fantastic RPG game, but the setting is superb. Sun dies, and whole humanity start to live underground in cities together with other races... It has an awesome setting, awesome gameplay and awesome story)
System Shock 2 http://www.gamespot.com/pc/rpg/systemshock2/index.html
(Humanity makes its biggest exploration in space: Towards other planets. But (as usual) the great exploration spaceship suffers strange happenings. An inspirng story with many philosophical messages, extraordinarily good)
well, that's all that comes to my mind right now
computer game is the new media, is the art!