Nolan is a fine director, and I wouldn't exactly call him that overrated (maybe slightly). Is he in the league as Kubrick? No, but who is now a days? Maybe PTA might come the closest, but I am sure I am missing someone. That said back to Nolan.
It seems Memento is well respected by most posters, and I strongly disagree that Inception is garbage. It does have issues, but the issues do not warrant such a strong disclaimer. While I think DKR was overrated by critics, I also think Insomnia is a overlooked gem and his other non-Batman movie The Prestige was quiet excellent. My only issue with Nolan is I want to see what he does post-Batman (Interstellar looks right up my alley). I just don't feel we have seen enough yet (even Kubrick had many movies in before he saw him at his peak), and I would like to see him do smaller work again (like Memento and Insomnia).
Also I know it is quiet the hipster thing to say QT is overrated, and he copies this/that (if that was your issue than every director is overrated), but he has made some of the most enjoyable movies in the last 20 years. Even at his lowest, Death Proof, he saves it once the movie ends up in Tennessee. I would agree that QT is a better writer than a director, but I wouldn't want anyone else directing his movies. Of course he will never be the director Kubrick was, but he is not that type of director (Kubrick was an artist).
My overrated? Woody Allen is a easy one of course (I did like Match Point), but I would say Francis Ford Coppola maybe (who I loved in his prime). What I mean by this is he made movies on a high level for awhile, but boy did he drop off fast. Other names that pop to mind are Frank Capra, Roman Polanski, Tim Burton, and John Cassavetes.
Another name I would say is Spike Lee. I think he has directed 22 movies, and out of those 22 I liked 6 (Do the Right Thing, Malcolm X, 25th Hour, He Got Game, When the Levees Broke, and Bamboozled). Not a good average at all. To be positive I think Bamboozled is criminally underrated, and an amazing satire of racism.
Also to throw this out there I think Hitchcock is a better director than Kubrick.
Edit: I heard discussion on a Podcast where someone was saying that Scorsese's work in the last 10 years or so is overrated. He made some good points, like he has pretty much made basically the same movie over and over recently. While I didn't agree with his thoughts, it did make me think. I guess I didn't agree because Scorsese does it so damn well no matter if there are similar threads in his movies.