You point out that GTAIV had no effect on ps3 hardware, but forgot to mention that it also had no effect on 360 hardware. Then you point out that Halo 3 DID move 360s, but for some reason discount MGS4's ability to move consoles. And MGS4 DID move consoles in Europe. Sales rose almost 30% over previous weeks. And that's in the territory in which the ps3 was already selling the strongest.
You could say that GT5P had already caused a lift in the EU, and that carried over a bit until MGS4. GT5P, unlike MGS4, did much more for sales in the EU than it did in the other territories.







