Damn, I always toss MGS and MGS3 around. It's hard to pick a favorite. Hmm...I'd probably go with MGS3 as well because of the survival and camouflage aspects, along with the CQC and boss battles (The End and The Boss), though I love MGS's bosses more. The nostalgia factor with MGS is the highest for me though since I've been playing it over and over since its initial release.