I'm not doubting adding networking adds complexity. I don't think the comparison of complexity between the graphics and AI of gears of war vs the networking of Yegge's game is easily made. The interesting thing about Gears of War is that most titles of that caliber take a lot more than 500k lines. Yegge's game as a comparison point seems pretty fair to me, and I just don't buy the fact that the extra networking necessarily makes the code so much more complicated than Gears of War - thereby invalidating the comparison.
It's not the networking. It's the fact that changes need to happen at runtime, and sync to any number of clients that may be watching.
Also, your hypothesis that the prettier game the more complicated one is false. 2D physics and AI can be horrendously complicated, or elegantly simple. There's no way to tell just by looking at the game, except on a very rough level. Take the game Gish for example. I don't know how complicated that little blob's physics is, but it could be extremely tricky.
Amusingly, the game rules are the least complicated component.
I meant syncing the game state to be included under the term networking. Amusingly, Yegge's post about the length of his game was all about how massively bloated it was because of Java. His own estimate of what size he would like the game to be was 150k-200k. Apparently impossible in Java, but presumably what he felt he should be able to achieve that even given the game's distributed state management.
