Update: I was unfortunately not aware of Shamus Young's severe criticism of Fallout 3 available here to link in the original piece and I regret that. It dovetails rather nicely with what I've written and it's much better executed than my piece. I strongly recommend anyone...
The Good: Fantastic story, smart AI, great level design, fun and challenging bosses, nice easter eggs
The Bad: Snake takes a back seat, no guidance, too much trial and error, cut scenes are way too long, too much backtracking
This game kind of haunted me growing up. Everyone was raving about it, it was always rented out at Blockbuster, I saw commercial after commercial for it, but never understood it. I finally bought it when it was in the bargain bin years after release and was still too young to understand the game. It was confusing and I didn't have the patience for stealth games. Now that the HD version has been released I figured I would give it another go. The game is fantastic, has a memorable story, and some of the best stealth action out there and holds up well for today. Honestly, if this game had current graphics you wouldn't be able to tell the difference.
The game is made up of two chapters, one in a tanker, and one on Big Shell. The tanker section is the shortest and this is the only time you play as Snake. You are introduced the basic controls and gameplay which is pretty simple. The controls are a bit hard to get used to and aren't planned out very well, but they work. The whole point is to get to your objective without being seen. You can knock out guards through melee, drag their bodies into lockers to hide them, use tranqs, or just plain old head shoot them with a silenced pistol. This stuff isn't just handed to you though -- you have to go find these weapons. The game also has exploration elements, but this can really frustrate some people because you have to use a lot of trial and error to get through some spots and find out where to go. The level design is really great though and each section is small enough to memorize very quickly. If you die you restart that one section instead of going back a ways. I really liked this a lot, and you are allowed to save anywhere you want. The stealth elements really take getting used to and feel stiff in spots. You can't kneel and walk at the same time. If you crouch and move forward you go into a crawl. You can hang from ledges with a stamina meter, go into first person mode for accuracy, climb boxes etc. This all adds up to being tools to use for the stealth experience. How you use them determines how well you get through each section.
Each section is completely different, but you can't just run around killing everything. There are guards that have to check in every minute or so and if you knock them out and they don't respond a response team will come check it out. If you are spotted your radar disappears and you have to go into a cool down mode while the enemy searches for you.
The AI is great in this game, and you can really tell how far ahead the game was for its time. It gives you a sense that you can't screw around, you can't exploit the AI, you can't exploit the levels, you just have to do things the right way. You have to memorize enemy patrols, figure out where the cameras are placed, use chaff grenades, hide in boxes etc. Don't worry though, there is some action in the game in the form of great bosses.
Fighting Vamp, Olga, Metal Gear RAYs, and a Harrier II are all exciting. The bosses are great and you can tell they don't make them like they used to. Health slowly widdles down, you have to stay on your toes, and healing items aren't thrown at you constantly. You have to memorize the enemies moves and patterns then find what weapons works the best. The Metal Gear RAY fight is extremely tough, yet somehow very fun. You have to constantly dodge and roll and quickly switch to first person and then roll around again. Using the high frequency blade uses the right analog stick to swing the blade around which was very unique at the time. The game is highly cinematic and was probably the most cinematic game ever made at the time. One thing I have to mention are the long cut scenes. They can be over 10 minutes long towards the end. You will go through real-time cut scenes then 5 minutes of radio dialog. It's not necessarily boring, but the ADD in you will want to do something else while you listen.
Metal Gear Solid is also known for extras that are hidden for fans. Things like Zone of the Enders boxes and posters, strange little things that you can do that will trigger dialog from your radio, these things aren't really seen these days. Most developers don't put the time or effort into doing these things even though a select few will only see it. Most people may not care, but I like seeing little hidden easter eggs everywhere. This game will only be enjoyed by the patient though. Running around everywhere trying to kill everything isn't going to work in this game, but I did hate the lack of direction. If you didn't know any better or check a FAQ you will run around aimlessly not knowing what to do. Especially when you try to disarm the bombs in Shell 1. There are quite a few and each bomb is tough to get to. Half of them I just couldn't find and the other half were a pain to get to. If the game had a bit more guidance it would pretty much be perfect, and don't forget the weird controls.
As it stands, MGS2 is one of the greatest games of all time for a reason, it's a perfect symphony of story, cinematics, stealth action, action, great boss fights, pacing, and character development. The HD upgrade for Vita and PS3 adds texture filtering, some aliasing, and even some reworked textures. It looks very smooth and crisp, but still looks dated. If you can look past all that you are in for one great game.