Personally my entertainment comes from just exploring the GTA maps, searching for easter eggs and the freedom of 'free roam' and online play. The story, although I'll no doubt enjoy and which I'll complete befor I take it online comes a close second for me. It's been the same for me with GTA since GTA III, R* just gave me a unique gaming experience of doing wtf I liked and when I felt like doing it.
Also, I heard Amy Winehouse was making a cameo role for GTA V but that's gone tits up now. < not true