watching this confirms mgs1 as my favorite mgs. the memories, the story, the characters, the bosses, the stealth, the codec portraits, SNIPER WOLF. I don't think it's the best one (this is MGS2 Substance for its GOAT vr missions) but it has the full package of what Metal Gear stands for.
Other top contenders are MGS VR Missions, 3 Subsistence, Metal Gear 2, and Ghost Babel.
MGS1 stands as my favorite MGS because it literally changed what I what I thought a video games were capable of. FFVII already made a big impression, and the next year I was playing MGS where every line is voice acted and it felt like a Hollywood film in game form. You can say a lot about MGS series, but MGS1 still stands as imo, the first complete package in terms of video games as an entertainment medium. There were other games that were voice acted before MGS1. There were games were better stories than MGS1. But no game tied together the storytelling, with such tight gameplay in such a cohesive manner before it IMO. It's just the complete package in every respect for me. You could point to Half Life and say that but while I understand that POV, I disagree with it. MGS1 pushed games ten degrees forward. I felt that way when it first came out and I still feel that way now.
Even in 2016 it's still a fantastic game. Its art direction despite the limitations of the original playstation is jaw dropping even now. Like how the metal panels on the walls shine. Or the lights on the ceiling. Or the lighting in the genre. What a fucking game and complete masterpiece.