Hmm to be honest I can't decide which game is my favorite of all time, since they're so many games but I really like L.A. Noire. The Story surely wasn't that breathtaking or the Gameplay (except for deciding if someone lies or not) wasn't something new, too. In my opinion the technology used for creating it and making the People like really people amazed me at this point. Also the Setting in the golden twenties was great designed I felt i've really been there. Btw. you can watch how it works on the IGN Tech Trailer.
Red Dead Redemption was great too (somehow.. both are from Rockstar. ) I've never played as a "Cowboy" or before. The world was detailed, the Minigames were fun and you couldn't resist John Marstons charm. I know how my heart literally broke at the End when he got out of the barn and tried to take some of the guys with him to afterlife and died. I didn't like it to play as his son, so as soon as possible I had finished to kill John Marstons last enemy as his son, i saved and turned it off. The DLC Undead Nightmare was nice and fun, but nothing compared to the original game.
»Don't ever be ashamed of anything that makes you happy.«