I don't really play enough at the moment to get bored with GTA. I'm slowly progressing through the story line. But I like to take out my road rage and stress from the day on innocent civilians in the game. I can have fun for about an hour or so a week just going on rampages and chases and seeing how much damage I can do.
Also so far the story line has been very fun to play. But I have always been able to get few hours of fun out of all the GTA games. This games has alot of little things that make it great.