- go to the control panel>Game Controllers>Properties>Settings>check the box "swap joystics"
- launch the game. Go to the control settings>controller and enable "left-handed sticks".
- enable "invert y axis" too.
Now your left and right sticks work properly. (Dont forget to disable swap mode if you want to play another game =))
To fix the other buttons' mappings you must edit the WarInput.ini in the My Documents\My Games\Gears of War for Windows\WarGame\Config