Very early stage and just to try and visualise what I had in mind for it. It should be an identification for the game, a trademark that will allow recognition.
ANGELS & DEMONS (alternative Angels & Daemons)
[edited spelling error]
Some sort of demon horn, or devils horn rising upwards and on the outer edges of the horns (that look like the top of the Q in Quake 1, there should be angel wings attached in 4 or more sections thus forming a unified symbol for Angels and Demons in one. The A&D can be placed inside of the logo i.e symbolizing good to evil. A&D could be read from up to down and entwined together, like a grapewine look.
Best solution would be to use as few colours as possible, preferably three, or even less. Use of vector or even a 3D render could be made. The wings shouldn't be to 'cluttered' as they are in my test [edit: removed] nor should they be as pure white since the logo would fit nicely on white background.