I see I have something of a reputation, haha.
But no, seriously. If you understand the game mechanics on a basic, fundamental level, a brief look at his tools will reveal why he is considered a top tier character. Going into more depth just reinforces that view. Gen Fu has some tricky secrets, but you don't even to know them to understand why the character is such a threat. Knowing will just solidifies that position even more. The meta-game discussion then sends it into overdrive.
If you don't get that, I think your confusion would derive more from lack of game knowledge rather than lack of knowledge about Gen Fu. If you understand the game, you will look at Gen Fu, and you will see it. If you don't, you have a lot to catch-up on, and there are plenty of better places to do that than this thread. I'm not sure any amount of my explaining things here would do any good if you don't understand the fundamentals (as well as some of the important nuances) of the game's mechanics and workings.