MGS 1 is, even to this day, unbelievable. It tried (and succeeded) in doing something new, and given the PSX's hardware limit, it looks absolutely incredible. yah, it can be pixelated at times but I felt totally immersed in the Alaskan military base environment.
But MGS2 is just a total waste of time. The story is crap, the tanker was cool, but the oil rigs suck. I don't mind Raiden as much as most people, but he still blows compared to Solid Snake. Overall, a very very weak sequel and Splinter Cell has shown us what the evolution of Stealth based 3rd person game should be like.