Which game should I buy for my xbox 360?

Hey! I am leaving for EB Games in about 20 minutes. Please help me! I am an owner of an xbox 360 and am looking for a great game! I have M Effect and Halo 3. I was choosing between either in's creed and burnout paradise, but aren't fixed on either. Should I buy one out of these two? Or buy another game? Thanks in advance!