Nothing in terms of relevance.
For example last year they gave 3 perfect scores to Super Smash Bros Brawl, Metal Gear Solid 4 and 428: Fūsasareta Shibuya de. In my opinion these games don't deserve that high score, at best I would give them an 8 or 9 out of 10.
By the way I don't say Monster Hunter 3 doesn't deserve a great score, the game looks amazing, but not a 10 or a "40" in this case.