What Makes Good Gameplay?

Last night a friend mentioned a gameplay design philosophy. He said, "Simple, but deep = good gameplay." Or something like that. I immediately responded to him with something like, "Why does my underwear smell like poo?!" Or something like that. Then I told him that that design philosophy was genius.

And now it is today! And now I believe that that philosophy is (often) wrong. Or at least the "simple" bit. I also think "easy to learn" in "easy to learn, hard to master" isn't the perfect over-generalization of good gameplay design either. A lot of the best games, ever, have been hard ones to learn, due to their not being simple. My two favorite RTS games, for example -- Company of Heroes and StarCraft (2) -- require a lot of memorization time (not merely skill mastery time, of which they require a lot, specifically for the multiplayer). Those RTS games require a lot of knowledge not quickly learned (if learned at all) without reading or listening to the advice of pro gamers. Knowledge isn't skill; yes, I actually believe this.

But I do agree with the "deep" and "hard to master" parts of those design philosophies. Those words conjure up images of meat. And I like meat.