We all know that Rockstar Games' Grand Theft Auto IV is going to be huge when it hits retail on April 29. Janco Partners' Mike Hickey recently predicted the game would sell nearly six million in its first week, racking up $360 million in revenues and potentially stealing thunder from Iron Man at the box office.

Now Hudson Square Research analyst Daniel Ernst has done Hickey one better, predicting (as part of his massive fiscal '09 outlook report) that GTA IV will be the No. 1 selling game in all of 2008 with a total of 13 million copies sold. According to his estimates, this will top blockbusters like Wii Fit (10 million), Super Smash Brothers Brawl (9 million), Final Fantasy XIII (8 million), Madden NFL 09 (7.5 million), Gears of War 2 (7 million), Call of Duty 5 (7 million), Guitar Hero IV (7 million), Metal Gear Solid 4 (6 million), and others.

"With its proven track record from prior iterations, we expect Take-Two's highly anticipated Grand Theft Auto IV to be the top-selling video game of 2008. We believe the title will be a driver for PS3 sales, and we expect strong uptake from Xbox 360," said Ernst. "We also anticipate a strong performance for Nintendo's Wii Fit. Wii Fit has sold almost 2M units in Japan since its December launch, to an installed based of more than 5.5M Wii owners there – an impressive 26% attach rate, in our view."

He added, "Our analysis of the performance of the top 20 titles suggests that these 20 games comprise only about 25% of the estimated annual video game (software revenues), in our view. This is contrary to the historically-accepted 80-20 rule, which theorizes that 80% of revenues come from only a small fraction of the games. The 25% share suggests that the video game market is highly stratified."

You can check out the full top 20 breakdown and comparison to the top titles of last year in the chart below (click through to view full size).

GTA IV to sell nearly double Madden 09?