I guess no one told him, but the previous GTAs (I can't comment on the new one) don't so much have a story as a pastiche of other stories interspersed with random missions where you kill people for no good reason. No one is going to say that a game that stole its entire story from something else has good writing. (Well, idiots will.)
The other funny thing is that most people don't play GTA for its story, and the people that do go through the story mode aren't invested in it. Talk to someone who's been playing GTA for a while about what they've been doing lately. I guarantee their story will be about what they did for fun, and that it had nothing to do with the story mode.
I'm not sure why this guy is trying to sell GTA as a story game, since
- It doesn't have that great a story in the first place.
- People don't care how good the story is.