I'd say it's more about the world-building and what can happen in that world. Some missions are just simple point a to b, but others really aren't.
I just did a mission in GTA 3 where I rammed an armored car off the road repeatedly and then hijacked it while chased by police cars. It's that kinda movie-style atmosphere, where anything can happen, that's enjoyable.
I never heard anyone accuse gta storytelling as "pretentious" though.
The shooting mechanics are awful on PC though, I'll give you that one.