From Unify Community Wiki
This page serves as a cross reference between Unity and the XBOX 360 contoller buttons/axis.
Full controller support
If you only build your game for Windows, you may be interested in XInput.NET which allows full XBox 360 controller support.
Back = joystick joystick button 6
Start = joystick button 7
Press = joystick button 8
Right Analogue Press = joystick button 9
Analog Axis sensitivity should be 1, digital should be 1000.
Left Analog Horizontal = X Axis
Left Analog Vertical = Y Axis
Triggers = 3rd Axis (Left: -1 - 0, Right: 0 - 1) _ (Left Trigger Axis: 9th, Right Trigger Axis: 10th (Both axis are 0-1))