In fact MGS 4 is an awesome game, i really think most of it's cutscenes are in-game graphics, the only one i'm with doubts is the one where they show the two eggs that sunny is cooking, that seemed too real to me, thanks to the shine one the eggs, and the reflections on it's surface, but i can be wrong ;).
Also, i don't know about gears2, but gears 1 i think it's almost all in-game cutscene, just like the HL one's and mgs 4 one's too.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
