Gears of War has still yet to equal the sales of MGS 2, though it could certainly do so at some point. MGS 3 didn't sell quite as well because people were turned off from their experience with MGS2. It still sold 3.96 million plus however many copies of Subsistence were sold (VGChartz only has Japanese date for that version).
It looks like MGS 4 will be coming out in June, worldwide, if a leaked advertisement is to be believed. The PS3 could be around 12 million at that point (random guess, someone else can figure out sales rates - could easily be much higher thanks to GTA IV) and I could easily see MGS 4 reaching 4 million before the year is out and reaching lifetime sales of 5.
The real wild card is how well Gears of War 2 will do. Will Microsoft launch another super huge advertising campaign? If so, GeOW 2 could easily sell another 5 million plus.







