I've been in a few game-making teams, and it's disheartening to see people arguing about whether someone is a better coder because they work on graphical 3D games or roguelikes. To me, a good coder is the one who gets good work done. Some are more experienced than others, some write code at a faster rate, some write cleaner and more readable code, some write more stable code, some have better problem solving skills, some have more mathematical knowledge, some have more knowledge of advanced algorithms, some are better at working near the hardware level, some are better at making critical engineering decisions - all these things and more are factors. For modern AAA games one good coder is not enough, even if it's John Carmack, and even if you have the Unreal 3 engine to work with. You need a whole team of good to great coders, who work well together, or you won't get a good result in a realistic time.
Programming a fully playable standalone game in under 7 days tells me that Kornel is at least a good coder, maybe a great one. But that doesn't really matter, it's the design skill that goes into his games (well... AliensRL at least) that make me play them, and thus join this forum. Which is as it should be, IMO. After all aren't Roguelikes supposed to be all about the design, by imposing very simple and restricted graphics to work with?