It's missing some things in the game that would have made this more awesome to play. I don't know why Rockstar didn't include these things but here's what I think is missing that should be in the game:
Customizable homes in single-player and the ability to buy them.
Police acting like real policemen (example: running a red light in front of them)
An actual gang war mode (like San Andreas involving taking over territories in the city)
Alot more heists side missions