Well, I've always wondered why most CP's have the joystick on the left and the buttons on the right. Assuming that most people are right-handed, you would expect that the most important control (the joystick) would be operated by your right hand, and the less important (the button) with your left. When I use a joystick (Suzo Competion Pro) for my Atari 130XE, I always control the stick with right hand and use the left button for firing. Also, the Jakks Ms. Pac Man I bought recently has the same set-up: buttons on the left.
I have configured Galaxian to use my P2 (Right side) joystick, and use the right-most button of P1 as fire. It feels much more relaxed this way.
I also play Ms.Pac Man with the P2 (right side) joystick because it's very close to the center of the screen. This is a great substitue for a dedicated stick in the center.