I laughed when Microsoft chose to put the right analog and left analog diagonally from eachother (I owned a PS1 and N64 at the time so it was new to me). Now having owned a 360 for 5 years, and having bought a 360 controller for my PC games, I can definitely say I was wrong and it is the most comfortable controller ever. It is curved just right, it weighs a good amount to not feel cheap, the triggers are the best in the business, and the analog sticks are high quality and offer more grip then the dualshock 3 and Nunchuk.
Microsoft copied GameCube diagonal analog stick placement.
It might have been your first experience of that since you did not have a gcn. But Nintendo was first. And that GameCube controller... Is legendary. I do prefer the 360 pad to the playstation one though.
The 360 pad feels good for fps games. But it suffers badly for fighting games with the atrocious dpad and the angle at which your hand holds the right side where the most commonly used buttons reside on the face. 360 game pad is basically the old OC sidewinder game pad that came out after Nintendo GameCube showed the world how to build a controller (what IS it with the purple color though?...)
The gcn controller had it all thought out.