The GTA games to me have always been more about the experience than the gameplay itself, which admittedly has strictly followed the somewhat repetitive formula for a long time now. I like the way it allows me to believe I am living the life I can't and won't in real life for obvious reasons. It's fun to be the bad guy after all. Also, I enjoy the silliness and tongue-in-cheek nature of it all while it still manages to play it somewhat straight.
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” - Mahatma Gandhi