Amazing way to wrap up the series main storyline.
Gameplay is at its best
Camo is no longer a burdon to change (unless you change to one of the more battle ready camos)
Amazing story
Gunplay is much better than previous titles
Nostalgia
Multiple paths
Ability to play the game however you want (sneak, or go all ape on everyone)
Ending: Mind=blown
Many WTF moments
Bad:
Last "act" in the game has very little gameplay.
Nanomachines are a common cop-out from explaining things in the story.
The BB's are basically like the Cobras from MGS3
Separate install times for each act.
Story: 9/10
Basically the story is the most important part of an MGS game. Most of the games do a great job of balancing story and gameplay. This one does so too, until the last act however. This is not that big of a problem as the cutscenes were amazing and will make you forget about how little gameplay there is in these parts.
However there is a reason why it's called Metal Gear Solid "FOUR." I would not recomend playing the game unless you play MGS1, 2, 3 and three or download the database or read many summeries and wiki's about those games. I had played those 3, and the story was mindblowning an answered a ton of questions, but I did notice that those who have never played the previous games would not be able to relate to a few characters. You may even find it confusing.
Overall, most MGS fans will enjoy the game, and while newcomers may like the story, they will have many questions, most of which can only be answered by the past games.
Gameplay: 10/10
This, this is what makes the game so great. The controls are good, and most of the gameplay mechanics adapt to the games many environments. Weither you are sneaking through a total warzone, trying to infiltrate a run down mansion in order to get into a lab, or revisiting a long forgotten place, the controls, wepons, AI, and everything adapts. The shooting controls have gotten much better too, when you are spotted you no longer have to stand in first person mode while standing still just to get that headshot, in fact, first person mode is hardly used, because the third person aimer works so well. The cardboard box trick works better than ever. What I mean by that is, when someone lifts up your box it is very easy to just press R1 and choke them or throw them to the ground knocked out. The controls are completley different, but work much better than the older ones (though I still sometimes find myself pressing circle to punch...) Theres also the camo system back, only its much less annoying. You no longer have to go to the start menu, just lay down or press up or stay in an area for long enough, and your Octocamo suit changes to fit in with it's environment.
Sound: 9/10
The sound and music is very high quality. The only annoying thing is constantly hearing AUUGHH!! in a warzone area.
Graphics: 10/10
I'm not really a graphics whore, but the graphics here were amazing. There's so many little details in the game that make the graphics really stand out. There may be better graphics out there on the PS3 now, but this is amazing.
Overall should you get this? Yes you should. In fact, this game is in my top 10 along with MGS 2/3 and Super Mario 64 and OOT. However I would recomend playing the older ones first. They are great games just like this game, and the storyline to this series is one of the best I have ever heard. You don't have to play the older ones, but it would be a good idea.