It's expected. Same thing to an extent happened to Gears 3, which was the best Gears IMHO. A third title in a franchise that's grown huge often (not always) gets lower scores as some reviewers move into nitpick mode.
Batman is likly to be this years Uncharted 2, a game seen as making a big leap from first release to second and also a new IP for the generation. You can see with Batman, as with Uncharted 2 before it, that even where reviewers nitpick they are not translating that to the score. Uncharted 3 won't get the same treatment. Gears 3 didn't and it's nothing specific to Uncharted, just a commom pattern you see in the industry.
There are of course exceptions to the rule, but I wasn't expecting Uncharted 3 to match Uncharted 2, even though reading through most reviews (including the 8s) it's seen as a better game.
Timing and market position plays a part in getting above 95% on metacritic and this year that timing is and market position is with Batman (which is bloody great BTW).
Try to be reasonable... its easier than you think...
