Not only that, but there are WOW HOLY FCKING SHIT moments in the game that are lost if you havn't played the previous games in the series.
The problem is, how do you convince a non-believer aka MGS skeptics who have very little experience with Metal Gear, that playing through literally hundreds of hours of gameplay(and cutscenes!) is necessary before plunging into MGS4 on the PS3.
I was playing through the MSX version of Metal Gear again recently, and kept wondering how many people actually took advantage of these games on the Subsistence disc and played through them from start to finish. They are fucking awesome!
MGS4 is one of the greatest game experiences ever in video games. I have seen people on other message boards talk about all types of franchises like Sonic or Mario, etc etc and will say things like "why can't they just to this". MGS4 is basically the greatest fan service game ever conceived. There are moments in that game that will literally smack you in the face, leaving you screaming at the TV "Holy shit, I can't believe that just did this!!". Provided you of course have played through the other Metal Gear games!
(P.S. - Please watch all of the cutscenes. Please. Drop your cellphone, stop checking your email, cease hitting the refresh button over and over again in the browser, or reading twitter or some syndicated blog. Calm the fuck down this one time, grow an attention span & some patience to watch the cut scenes in these games. It is part of the experience, and if there was ever one game franchise that should be allowed cut scenes of this length.... its Metal Gear.)