In this thread: http://chowhound.chow.com/topics/480608 which was revived a couple of days ago, Zin1953 suggested that the subject of Right Bank Bordeaux be treated as its own thread. I tend to agree, so this is my response, that I will link to on that thread.
I have never had Petrus. The Le Pin and LeFleur I've had have been underwhelming. I've had historic vintages of Cheval Blanc (lots of Cab Franc in there) without loving it. The one right bank Bordeaux which always springs to mind when I'm asked this question is Angelus. I don't know the typical blend, though I think this is a wine heavy in Cab Franc. There simply is no 75%+ Merlot from Bordeaux that stands out to me as a clear favorite.
Interestingly enough, one of the more notable things about Chateau Palmer (Margaux) is that it is famously high in Merlot. It also happens to be one of my very favorite left bank wineries.