I constantly confuse the button placement for circle and square.

360 controller is basically a SNES controller, although I do get confused with the multiple shoulder buttons sometimes.

I would assume that the shapes were meant to break the language barrier, since the majority of people outside of japan cant read the japanese alphabet, and they most likely cant read ours. When they see an xbox controller they most likely are like wtf is up w/ these wierd shpes, why cant americans use simple shapes like circles and triangles. Btw xbox1 controller(whats up witht the black and white buttons and where are they?) is basically a dreamcast controller and the 360 controller is just a dualshock controller with the directional pad and left joystick switched.

the only problem with this theory, is that Nintendo had been using A/B for a long time, and was incredibly popular with the NES, SNES, and GameBoy. As I already stated, it was probably due to trying to avoid patent infringment.

I grew up on Nintendo buttons but when I made the move to Sony I had no problems. I've been using it for over 10 years now so I'm pretty use to the button lay out.

That's the thing, I HAVEN'T memorized ABXYs position either.  I'm an old gamer, I'm an early 80's kid, the good old NES days.  Usually on a QTE (that's guick time event, right?) for a nintendo or xbox controller, I repeat the buttons in my head as I move my thumb on the 4 buttons.  like in my head I would say A while my thumb is on the A button, B in my head why my thumb is on the B etc.  In a QTE I say ABXY probably once every 2 second while moving my thumb, for the whole QTE.  So if the QTE lasts for 30 seconds, I would have said ABXY while moving my thumb around 15 times during.  That's the easiest for me ABXY ABXY, constantly saying this in my head during a QTE has more flow than triangle, x, cirlce and square I think it is.

Lets see if I can remember without having the controller in front of me.

top - triangle
bottom - x
left - square
right - circle

did I get it right?

^ yes

Feels dead natural to me and I started with SEGA. At first I just remembered the colors but now it's colors or shapes. Didn't take much time to get used to either.

well i have been a PC gamer for more than 15 years and in the old days most of the games didnt even get a symbol for the action and function buttons and some of the games hadnt any keys customization... so i had to learn lots of key layouts... i only use the PS controller and from where i come from it is easy as bananas!

Haha, i'm glad i'm not the only one.  I grew up on NES and Genesis so letters for buttons was the norm.  When the PS first came out I thought the whole using shapes thing was a goofy way to make yourself seem different imo.  I've never owned a Sony console so I've never gotten used to them like second nature.  It's a minor issue though.  It only affects me in football games where you have to quickly pass the ball to a receiver that's assigned to a button or during QTE's when the X button pops up on the screen and I hit what would be X on a 360.