Absolutely the best game I have played yet. I don't consider myself a Sony fanboy, but if you were to call me a MGS fanboy I wouldn't be able to argue with you. I even have Solid Snake tattooed on my leg. That being said, 4 does an amazing job of completing what has amounted to a truly epic story. It has completely rounded out the MGS series, as well as including storylines from the original Metal Gear games. The cutscenes are long and many but I cannot imagine any other way of giving us that much information, and I loved them. As greenmedic88 said about the controls, I too think they are now refined to perfect, though I enjoyed each installment that came out at least 20 times over each.
I took a leisurely 16 hr playthrough the first time around, enjoying all of it, except for the little trick they play on you in the ending(I cried... no shit!) When I was finally done I sat back and let it all sink, before deciding what to do. My options were to immediately replay it or go through the entire series. So that's what I'm doing now, just finished MGS1 and now I'm on 2, then on to 3 and once again I'll play through 4. After that's done, I have to get all the weapons & emblems, though I'm not to sure about the Big Boss one, that's going to be hard.
The ONLY problem I have with the game, is that this time around it might actually be the Kojima's last. 
EDIT: @ Ben, yes the Rex vs. Ray moment was friggin awesome!!! I'm gonna have to remember to keep that save next time around so I can go straight to that fight, woohoo!
