use "MultiGame ISO Creator v3.2.4F+" to add like 3 ISO's or GCMs to one image and burn it to have a multi-game disc.
As far as I tested (AFAIT?!), multi-disc games dont work this way, so you have to burn RE4 on separate discs or MGS:TS.
I burnt it on a Princo DVD-R at 4x and worked like charm, and beware on games that you choose to shrink since some have problems (there is a wiki regarding to this, g00gle it).