Considering that Perfect Dark: Zero was in development for 10 years and that it was touted by many as THE killer app for the Xbox 360, I'd say that a ranking of 87% on GameRankings.com is kind of a disappointment. What's really interesting is GameSpot's review is actually the second highest rating there (some site called Talk Xbox gave the game 97%). GameSpot is normally on the low end, but I guess in this case they just really liked it. It should also be noted that as of this post, IGN Xbox hasn't had their say yet.
Also, some might say Kameo is getting good reviews. But that kind of depends on what your definition of good reviews is.
How does 77% do for you?
I stand by my original statements. It appears so far that while Rare doesn't produce absolute crap, Perfect Dark: Zero is no Goldeneye (or even Perfect Dark) and Kameo is no Banjo Kazooie.
And let's also keep in mind that Star Fox Adventures initially had really high reviews. But you'll have a hard time now finding many people who still think it's great.