Good stuff.
I wonder if we are missing a dimension? (beyond Depth, just added).
Hero/Champions is potentially a very complete, elegant, and flexible game.
3E also does seem to be more complete, elegant, and flexible then 4E.
But I am not looking to play either any time soon.
CoC has some truly elegant mechanics, and can feel quite complete and flexible. A huge advnance for its time. But its not perfect: it really only works for certain types of campaings and scenarios, the % skill system doesn't work that well for variable challenges (though I like it) and as noted it does have some pretty quirky combat rules (which I think we normally ignore), You could even start the big argument that the d20 version, in part by cleaning up combat, adding more options, etc, comes closer to completeness and elegence.
But I am always up for a game of (BRP) CoC.
Why? It really works in play. The play experience is a little narrow, but very successfull.
This playability is why I like 4E over past editions. I can critique the game all day long in my head (or online). It doesn't feel as elegant, complete, or flexible as past editions. But it just seems to do better what we where trying to do before. I am not sure if this can be embeded in these other concepts, or is something else.