The answer to that question can be mostly summed up with three letters: Wii. Nintendo's console dominated online retailer Amazon.com's video game department in 2009, securing nine of the top ten spots on this year's bestsellers list.
Only one game stood between Nintendo and perfect top ten ownership, Infinity Ward's Call of Duty: Modern Warfare 2, which was #9 on Amazon's list of bestsellers, which includes both hardware and software.
Amazon.com's bestseller in the video game department was the Wii console itself, with the Wii Remote and Wii MotionPlus taking second and third, followed by the Wii Nunchuk. And, impressively, New Super Mario Bros. Wii landed at fifth, the retailer's bestselling game of the year.
Granted, Amazon.com does not represent the market as a whole, but the following list should be a decent indicator of what's selling well across all platforms, including non-Nintendo games like Assassin's Creed II, Halo 3 ODST, Left 4 Dead 2 and Uncharted 2: Among Thieves. Marvel at the top twenty below.
02. Wii Remote controller
03. Wii MotionPlus
04. Wii Nunchuk controller
05. New Super Mario Bros. Wii (Wii)
06. Wii Fit Plus (Wii)
07. Wii Sports Resort (Wii)
08. Wii Fit (Wii)
09. Call of Duty: Modern Warfare 2 (Xbox 360)
10. Mario Kart Wii (Wii)
11. PlayStation 3 Dualshock 3 controller
12. Wii Play (Wii)
13. Call of Duty: Modern Warfare 2 (PS3)
14. Wii Wheel
15. Assassin's Creed II (Xbox 360)
16. Halo 3: ODST (Xbox 360)
17. PlayStation 3 120 GB
18. Uncharted 2: Among Thieves (PS3)
19. EA Sports Active (Wii)
20. Left 4 Dead 2 (Xbox 360)