Yes because no game is perfect. I'm currently playing Metal Gear Solid 4, great game, but again, 10/10? No. Nothing deserves 10/10. Halo doesn't, MGS4 doesn't, not even Portal deserves 10/10. For a game to warrant 10/10, it must be PERFECT in every conceivable way.
I have never encountered a perfect game. Every single game has had some flaw in it. With MSG4 its the controls, and the way snake handles. With Halo, I would criticize its length and re-play value (for single player, that is. I've only ever gone through single Player with Halo 3 once, and it just didn't interest me after that).
Even the venerable Tetris has flaws. LocoRoco also had its flaws - the graphics got pretty samey after a while. Gears of War also has flaws, Rainbow Six Vegas has flaws, every bloody game has flaws.
And so none deserve a 10/10. Because every game has something annoying about it. COD4, on the higher difficulty, had some sections which were incredibly annoying because you kept dying and dying, and it was partially based on luck whether or not you survived. Mass Effect, great game, has its horrible menu system and graphical pop in.
Because no game deserves 10/10, I think we should just do away with scores. No game is ever going to be technically PERFECT. Instead, all reviews should simply list good points and bad points and let the player decide. Another thing about reviews is that they should be played by a member of the targeted audience. A puzzle-game fanatic is not going to give a shooter game a good score, for example.
Do away with scores. Simply list the good and the bad, and let the player decide.