Hmm...if richness and depth of character definition are what you're looking for, two systems come to mind. I haven't played either, but have heard many good things about the second, and have internalized a lot of the first over many years of reading.
The first, you already know, at least to some extent. HERO Games launches the sixth edition of the HERO System next month, and it looks like it's going to be a general reworking to get rid of some of the stranger bits and make character creation more modular and flexible. (Figured Characteristics aren't figured any more, COM is now a Talent, and it looks like many system elements are getting broken down and rebuilt as more streamlined, modular expressions of HERO's core principles, based on the advance news from Steve "Has Probably Written Another Supplement in the Time It's Taken Me to Write This Post" Long.)
A more 'indie' style that I've heard good things about is FATE, and you can check it out
here for free and legally.
EDIT: Sorry, missed Rule 3. Still, this is more an information post than an advocacy post.
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