Looking at the previous versions of the GTA franchise which all sold more than their predecessor, I'd say it could easily double MK. Just look at San Andreas.

It's simple really... GTAIV will be the clear winner in sales vs. MKWii simply because of it's install base (a current combined total of about 16mil for both 360 and PS3 alone in America) and the fact that it is up to this point the most hyped and anticipated game of this generation, even moreso then Halo 3.

That is not to say that MKWii will do poorly in comparison... far from it.  While i don't expect it to have a HUGE first week of sales in America (maybe a lil over a mil at the absolute most, but i could be eating my words in a couple of weeks) MKWii, along with Brawl, is going to have ungodly legs and will push demand for Wii even moreso since it will appeal to pretty much all of Wii's target audience being that it's very accessible and easy to pick up and play.  It'll be this year's version of Mario Party 8 where all the casuals will be picking it up because it's the popular game to get, and as a result most new Wii buyers will be compelled to pick the game up as well, maybe even moreso than Brawl.  We shall see though, but i think that pretty much sums up GTAIV and MKWii's expected sales performances.

@Cooguyev

The Ps3 version of GTA would need an insane attachment rate to beat MKWii

MKWii will have sold about 2M by the time it makes USA. Currently the preorders of MKWii are at 425K for USA. So let's say 500K preorders when it's out. It will sell at least 300K first week (other than preorders) so 2.8M

If MK only sold 1.2M more through the entire year (which is highly unlikely) it would still have 4M of sales. This is the very minimum I believe it can sell.

Can Ps3 beat that? Well, let's see

GTA isn't huge in Japan, let's say 100K for this year. It might make 150. Then there are about 12M Ps3s left to sell 3.9M games. That is an attachment rate of about 1:3, which is simply insane. 33% of all Ps3 owners would have to buy the game. And this is for the minimum of MK sales. MK could have sold double.

Wow some people here really overestimate Wii software sales. This wont even be close, GTAIV is going to trounce Mario Kart sales wise.

GTA IV

I had just read an article released yesterday about Grand Theft Auto 4 and more about Super Smash Bros. Brawl. The article spoke on how Wii had sold more consoles in the month of March (Last Month) then the 360 and ps3 combined. BUT they have also found that Super Smash Bros. Brawl had only sold 2.7 million copies so far. They have even found that the average 360 or Ps3 gamer buys more games than a Wii gamer.

 In conclusion, Mario Kart Wii and GTA 4 on their launch dates, we may see more of a close tie. In the end, I believe GTA 4 will actually beat MK in sales. Since the average wii gamer does not purchase a lot of games.

Washington (dbTechno) - According to figures released by The NPD Group, Nintendo managed to sell more Wii consoles than the PS3 and Xbox 360 combined in the month of March. This is all well and good, but the numbers also show that Xbox 360 and PS3 owners are buying more games, despite huge sales of releases such as Super Smash Bros. Brawl on the Wii.

Super Smash Bros. Brawl for the Nintendo Wii has managed to sell 2.7 million copies already.

This is only going to grow as Nintendo has many other releases in the pipeline such as Wii Fit and Mario Kart Wii coming to the U.S.

This diesn’t tell the whole story though, as the Xbox 360 and PS3 owners out there are still buying more games.

According to Wedbush Morgan analyst Michael Pachter, the average Wii owner buys 3.7 games per year.

This comares to 4.7 games per year for Xbox 360 owners and 4.6 games per year for PS3 owners.

Microsoft and Sony are both hoping that the release of Grand Theft Auto IV will further boost their hardware sales.

It is clear from these numbers though that even though the Wii may be leading console sales, the casual gamers who are buying the Wii are not buying as many games as Xbox 360 and PS3 owners.

ioi has said that the PS3 pre-orders for GTA in the US are 1.6m, couple this with roughly the same in Europe, if not more, and you have over 3m first week, which will mean it will clearly beat 4m with ease

 Why? Lord of the Rings trilogy on video made a killing on both DVD and VHS, does that mean that we should disregard one of the formats to make it "more fair" to other titles? Odd logic if I ever saw it.

I agree with you. GTAIV on either system > MKWii

Sorry, had to revive this due to the serious amounts of crow eating that will be done, if not by the end of the year then at the latest in January when Mario Kart passes GTAIV combined.