It took me 119 minutes to complete the campaign first time round and I got a grade C. In a first for me in 2 decades of gaming, I immediately played the campaign again, this time it took me 90 minutes and I got a grade B. I'm going to keep doing it until I get that elusive S rank - this will probably take a good few hours. MGSV is an excellent game and people really shouldn't get hung up on the main story being potentially very short (you can do it in about 15 minutes if you really thrash about) because the replay value is immense and there are a further 5 missions to complete once you have completed the main story - these can take about an hour if you are being methodical.
The graphics are amazing on the PS4 and the gameplay is fluid and a lot less frustrating than other MGS games, for the price this is a fantastic buy - it also comes with some bonus stuff for next year's Phantom Pain which is nice. Ignore the haters, this is an excellent addition and a real show of next gen power. You've kept us waiting Snake but it was definitely worth while.