Are you going to ignore the PS3 version of MW3? You do know half the fanbase is on PS3 right? Where as with San Andreas pretty much most of the same were on the PS2.
People know this, thats why they restrict comparisons between GTA and COD to a single console to make GTA's numbers appear larger. It's dishonest.
MW3 sold just under 28 million on 360 + PS3. Who cares if its across two consoles? That's what this gen has been about.