It has to be said, plain and simple: I have far more fun playing Devil May Cry 4 than Metal Gear Solid 4.
Despite Devil May Cry 4 receiving an 84 on MetaCritic and Metal Gear Solid 4 getting a 94.
In short, while MGS4 is by no means a terrible game, it's vastly overrated. DMC4 is, simply put, more fun (to me at least) than MGS4. That's all there is to it.
(Not that DMC4 isn't without its problems. It's got them.)