Well when people say things things like this I don't actually believe they mean Nolan is already at Kubricks caliber. In my opinion there movies aren't even that similar in concept. Nolan has more non-linear plotlines and action going on, which Kubrick doesn't make as much use out of. When people say these things I think they mean that in the future Nolan might the new Kubrick. So basically Nolan is getting on the right road but still miles away.
I love Nolan and Kubrick, it's actually hard for me to say which one I love more. I'd have to say Nolan has the better screenwriting but Kubrick wins it with directing. They are pretty different though I think.
I don't agree with Cameron to an extent, I guess he has things down plotwise but not storywise. He is pretty high concept but his things never live up to their premise, but I enjoyed T2. Scorsese is a god and so is Tarantino.
I've also noticed that Clint Eastwood seems to be getting better, it doesn't seem like any of his movies have a distinct quality but they are good.