There's a wonderful interview at Gamasutra with Hiroyuki Kotani, creator of Patapon — a game that I still adore, having snuck in quite a lot of time with it on my PSP.
The interview touches on a number of subjects, from how the idea for Patapon came into being and the actual development process; it's a fairly quick read at a mere four pages. On the simple versus deep conundrum, Kotani has this to say:
There's been a belief that a simple game can't be deep, and I think that a simple game can be deep; and, conversely, I think that a complicated game might be a shallow game, from a gameplay perspective — it just has a lot of complication. So, how do you see that issue, within development?
HK: The way I came up with a solution is to divide the game into two different layers. One is the very simple game, so that a player can clear the goal with just three commands. But for those users who want to play a deeper game, they can use weapons; they can collect equipment and weapons, to try to clear different missions, with different goals.
In addition to that, the basic idea of this game is about rhythm, so you have to beat the rhythm in the accurate way — and even though you are giving the command by beating the rhythm, you are also singing a song with the Patapons.
And so, it's not just a simple game: it's like creating the music with the Patapons, and that's what makes the deeper aspect of this game.
There are a couple of gems regarding game design later in the interview. Well worth a quick read.
If you missed our video interview from TGS, that's worth a peek as well.