Nine out of the ten biggest-selling games of the past 12 months are sequels, according to this Seeking Alpha piece.
Not exactly a shock, and it's a trend unlikely to go changing any time soon, with the likes of Gears of War 2 and Call of Duty: World at War busting the block this Holiday. Good spread of genres, though.
From the piece:
Here’s a quick look at the games that have sold the most copies over the past 12 months, in order of sales to date. (Note that the sales figures are approximate, and that the release date is the first date the game was released globally.)
1. Call of Duty 4 for the PlayStation 3, Xbox 360, and PC (10 million copies sold-Released November 6, 2007)-Activision, now Activision Blizzard Inc. (ATVI)
2. Halo 3 for the Xbox 360 (8 million copies sold -Released September 25, 2007)-Microsoft Corp. (MSFT)
3. Grand Theft Auto 4 for the PlayStation 3, Xbox 360, and PC (6.5 million copies sold -Released April 29, 2008)-Take Two Interactive Software Inc. (TTWO)
4. Mario Kart Wii for the Wii (6.5 million copies sold -Released April 10, 2008)-Nintendo Co. Ltd. (NTDOY.PK)
5. Super Mario Galaxy for the Wii (6 million copies sold -Released November 1, 2007)-Nintendo
6. Super Smash Bros. Brawl for the Wii (5 million copies sold -Released January 31, 2008)-Nintendo
7. Wii Fit for the Wii (5 million copies sold -Release December 1, 2007 (in Japan, later elsewhere)-Nintendo
8. Metal Gear Solid 4 for the PlayStation 3 (3 million copies sold -Released June 12, 2008)-Konami Corp. (KNM)