We've gotten wind of some disharmony in trying to run a certain Xbox game on the 360. These kinds of growing pains are to be anticipated initially, as we weren't expecting all the titles to work smoothly. Mortal Kombat: Deception is listed as being backwards compatible with the brand new console, but the guys over at TRMK.org have found out otherwise. After booting it up, they discovered that it runs fairly well up until the action starts. Once you start fighting, it just falls apart.
Sketchy polygons would apparently bleed through the drawing plane. At one point, the game even slowed down so much to redraw polygons that it made it completely unplayable. And how about this rainbow effect? If you managed to score a 360, have you tried playing some of your original games that are listed?