What they really need is a "pending decision" review option. This can allow you to give your initial thoughts on the game, providing as many positives and negatives as you can from your early hours with the game. Then, maybe a few weeks/patches later, you can settle down on a final score.
So many games are neg bombed early because launch sucks or a major issue may be game breaking. The game itself could be awesome. That 1 major issue however holds back that thumbs up. If you could say, I'm pending my final decision on what I think should they now release a follow up patch in the next few days/weeks, I will say thumbs down.
That at least gives more flexibility and if it's a launch title where I see a lot of pending reviews, it's because I know something is wrong with the game at launch and can very likely move towards a thumbs up in time.