I am a huge fan of Aronofsky. Give the man some time he is going to be around making brilliant movies for a long time. PI was amazing and I probably prefer it to Requiem, but both are very captivating and deal with interesting subject matter in a unique way.
The only problem I have with his work is in Requiem he overdid the hyperpaced frenetic cut-cut-cut-cut. If he interspersed that with some more long, flowing, tranquil shots (a la Kubrick, think 2001's space scenes) the fast paced cuts would have more visceral impact.
Still, for a beginner he is great. Any idea what projects are in his future? I've heard he is attached to the film version of Frank Miller's classic "Batman: Year One." I think a visionary with a dark style like Aronofsky could be one of the few people who could actually save that film franchise from the schlocky crap it has descended into.