I won't let being a couple days late to the party prevent me from saying that GTAV holds the title of most overrated game I've ever played. I got through maybe 15 hours of it and it was:
"We're crime guys! Let's go do crimes! Wow, we sure did screw up that crime! Now someone is stealing our lunch money and giving us a wedgie. But we're crime guys! Let's go do crimes!..."
Over and over again, broken up by the hilarity of some middle-aged guy's slutty daughter flipping him off or Trevor breaking comic barriers by banging a stuffed animal and pooping. Total Lulz!!
I'm not here to tell anyone how to play or enjoy a game, but I don't think very many people approach GTA expecting it to have some masterful, compelling narrative or anything like that. The missions are mainly there to set up action movie-like set pieces, I don't really think they're meant to be taken seriously as part of ongoing character-development arc or anything like that. I mean, there's even a point in the story where Franklin points out that he's still largely doing the same shit (dirty jobs for other people) after meeting Michael and Trevor, than he was before he met them. Besides, did anyone really go into the story thinking any of the characters would "see the error of his ways" and stop doing criminal shit? That would defeat the whole purpose of the game. Since their inception, GTA has always been a crime simulator (it's in the name ffs). The reason I have so many hours in the game is not because of it's amazing story, but because of how fun it is to around in the open world (which, say what you want about the story, the world is expertly crafted). Hell, the whole idea of the "open world sandbox" was spawned by the GTA franchise. It's even more fun playing in that sandbox with friends online, which is easy to do with an invite only session.
I see this game in much the same way I see Always Sunny in Philadelphia - it's about terrible people doing terrible things, none of the characters ever learn anything or become better people, and much of the humor can be considered crass or low-brow, but the way it wholeheartedly and unabashedly embraces that is precisely what makes it enjoyable (at least for me).