The way I see it is a lot of the mgs features are just a pretty version of things before it. Tenchu, as I said before, had you press a button you let you see around corners. MGS made you get on the wall. Granted it made the game a lot better, it improved game play a lot, and gave the game a more in depth feel to it, but how I see it it is just a pretty version of what Tenchu did. Sneaking from behind and killing people was in Tenchu, and in games before. Tenchu had various ways of killing from behind. MGS did breaking necks as the sneaking kill. It looked better and seemed more sensible than slitting throats stabbing in the back and other Tenchu features. (Slitting a throat isn't a silent death, there is a lot of gurgling, failing, and moaning). Crawling through vents and under various things sounds like a plat former to me and already done before sneaking concepts. Golden Eye had a lot of what was in MGS, the difference was Golden Eye was first person and didn't allow you to have the freedom and mobility as MGS.
Read through that, and look at how stealth games developed. MGS had the most features out of all the sneaking games that came out before and after, but those features were not created by MGS. MGS was the big one, if you notice the games that came out before it were not the type of game that could afford to be hyped before its release, which is why some of them went unnoticed. You turn a blind eye to Halo, which I see why, it isn't any thing special, but you know it got big because of hype. Well, MGS kinda did the same thing, except MGS series had a lot more going for it that halo did.
Hype is one of the things that make a game become great. It doesn't make the game good, instead it creates a community that wants the game and talks about it. A preexisting community before the game is released has people talking about it and ignoring the competition. That is why games Like Halo get so big, it's competition was ignored. That's why so many good movies get cast aside. that is why good music goes unnoticed. That is why good art goes unseen. This goes for games as well. It is another media where things get ignored simply because they were out advertised.
Look at Chronically of Riddik: Escape from Butcher Bay. The game made it where you could see in the dark, but you were blind in the light. This made for interesting game play. However, it picked a bad time to come out because the Halo hype wasn't over. It got great reviews from a lot of magazines and Tv shows, but sold bad because people were glorifying Halo.
Pure Originality has faded. Now is the time to make things pretty. Soon games will be left in the dust.