Its not just a problem with this game.
It pretty much big trouble in most of non Xinput, old DInput games with xbox 360 controller.
But i fixed this issue many years ago, when i had chilstream gamepad and wasnt able to use diagonal directions in Resident Evil 4.
Here you can read what causing troubles (to put it simple shape of minitick sorrounding is circle, but it inside square shaped field, so you cant reach corners of this square, that why you need to convert your gamepad from circle inside square, to square inside circle, to make diagonal corners reachable) how to do it and download required tools
http://pinnaclegameprofiler.com/forum/showthread.php?t=1208&page=2 if these tools will not work for you, try updated versions from
http://www.wingmanteam.com After this simple manipulation your 360 controller will be able to reach diagonal corners in every old game!