Exactly, why should we compared a spin-off of the Halo series to the fourth installment in the Metal Gear Solid series?

Of course it matters that it's a prequel. Sales definitely would've been higher had it been a sequel to MGS2. And Portable Ops is a handheld game.

And no, MGS1+2 definitely outsold Halo 1+2. The original MGS outsold Halo by over 1 million copies. MGS2 and Halo 2 are on par. Your only argument seems to be about opening sales which don't mean anything in the long run. Halo 2 had a bigger opening that GTA SA, but it was still outsold by 12 million copies. 

As for Halo being a bigger franchise, only in America. Overall MGS is a bigger franchise. with better sales. The Halo series garners more hype though, I'll give you that much.

Not the fourth installment, i'm talking about MGS3. It doesn't even have Solid Snake in it, logically it should be named Metal Gear 0 (a prequel to the NES games). 

I dont know where yall get your numbers from, but according to www.vgchartz.com, Halo 3 has already outsold all 3 Metal Gear Solid games. http://vgchartz.com/worldtotals.php And lets keep this on one platform cause Halo and Halo 2 also sold quite a bit on the PC

I love MGS4, but just because it's a big PS3 game doesn't mean it's going to be a block buster, or more importantly, a Halo sized blockbuster. Only two games have a chance of matching Halo 3's launch numbers this generation, and that would be Wii Fit and GTA4.

In fact, according to http://vgchartz.com/worldtotals.php Halo 2 has outsold every final fantasy game and every Metal gear solid game ever created including the heavily hyped Final Fantasy VII. The End

If we get completely technical, Even Halo CE has outsold every Metal Gear Solid game in existence. http://vgchartz.com/worldtotals.php

This thread is about launch sales, Immortal. And I have only mentioned launch sales about twice, but it has nothing to do with the argument at hand.

Portables Ops is a prequel, a spin off, just like Halo Wars, so why shouldn't they be compared using your logic?

MGS sold 5.59 million and MGS2 sold 5.56, where as Halo has sold 6.43 and 2 has sold 8.24 million. Proof: http://vgchartz.com/worldtotals.php

At the moment, Halo 3 has about the same sales as MGS3 Snake Eater in the others category. At the moment, it isn't that bigger and Halo 3 will probably surpass it next week.

Whether its a prequel or sequel, it is still the third installment in the Metal Gear Solid series.

Actually Halo 3 already has 6 million sales, above every Metal Gear Solid game ever created in the history of man in only 2 months and its still selling quite nicely. http://vgchartz.com/worldtotals.php

I said in the OTHERS category, Einstein.