Here's a list of the top ten best-selling games in the U.S. for the month of May 2013 from NPD group:

1. Injustice: Gods Among Us (360, PS3, NWU)
2. Call of Duty: Black Ops II (360, PS3, PC, NWU)
3. Donkey Kong Country Returns (3DS, WII)
4. Dead Island: Riptide (360, PS3, PC)
5. Luigi’s Mansion: Dark Moon (3DS)
6. Metro: Last Light (360, PS3, PC)
7. NBA 2K13 (360, PS3, WII, NWU, PSP, PC)
8. Bioshock Infinite (360, PS3, PC)
9. Battlefield 3 (360, PS3, PC)
10. Lego Batman 2: DC Super Heroes (360, WII, NDS, PS3, 3DS, NWU, PSV, PC)

Source