I was huge on Nietzsche in my 20's, red all his work, but outgrew him and became a Christian. He has some great and relevant ideas but he's not a systematic philosopher for a reason - his views are not consistent and many of them are based on unjustified assumptions. He has passion and rhetoric though which makes his stuff convincing, and yes he has genius.

His biggest fail is his materialism, naturalism, determinism and denial of absolute truth (which is a self refuting claim). If he were consistent with those his whole Ubermensch raving loses epistemic ground - why should anyone care about his subjective preference of what man should be? And since he's a naturalist and determinist why do ethics (what should one ought to do) matter at all?

He also ignored Hume's destruction of naturalism and basic bitch empiricism ("You can't get an "ought" claim from an "is" claim"). Even if we grant Nietzsche the world is in constant flux and organized around master/slave dialectic (which he got from Hegel), that wouldn't give us any reason to affirm such a world or system as good or desirable just on account of it being natural. In the end, he writes about his subjective preferences and makes a case why someone should care about them any more than someone else's preferences ("I like banana therefore banana good therefore everyone should eat banana"). No attempt at justified true belief there.