Metal Gear Solid 4.
Easily best game ever, and im not really even a MGS fan.
Completed it in 17 3/4 hours.
I highly recommend everyone to buy it.
It has some awsome little parts, ill try and describe one while keeping it spoiler free. After defeating the first half of a boss, he tries to read your brain but because there is no memory stick he cant, a boss from MGS1, he then tried to vibrate my controller and move it, the SIXAXIS controllers dont have vibrate so it didnt work, but with the DualShock 3 ones apparently he actually makes them move, not just vibrate, so i bought one of those.
Thats just one of the amazing features of the game. I could easily play through it a few more times, plus there is Metal Gear Online, which is pretty awsome.