I never really understand why people complain about this -- I'm playing through them now and the controls are fine.
Movement and combat are fine, the rest is not: attack+direction for combat moves is all nice and dandy, but why not a single key for interactions? Hey Mr. Developer, you choose to design a keyboard-only interface, i'm cool with that, but please remember that the damn device HAS OVER 100 OF THEM.
Same with the list based inventory; i feel it is often a subpar choice for an RPG, but at least in, say, Oblivion and Fallout 3 it is done decently... in G1 is an unecessary chore, both for the small screen space devoted to it and, again, for the keyboard controls.
Also GODDAMN DARKSIDERS WHAT THE HELL DARKSIDERS WHAT THE HELL
Myself, i found Darksiders quite enjoable with mouse&keyboard... i was just ready to fire up the gamepad, knowing it was a straight console port, but was surprised of how smooth i was doing with the mouse and stick to that.