Diablo 3 was fun for like a few weeks, but it becomes boring and ultra repetitive fast. You actually do the same 4 acts 4 times, each one increases in difficulty. On Hell ( or Inferno ) it became a throw the keyboard fest after enemies can faceroll you. I can attest as I was a day one downloader, and hit lvl 99 in Diablo II. I was stoked and into the Diablo franchise. This one also had some issues they have probably fixed, but trust me, it became boring even with new characters to play as.
GTA has a good story, lots of unlockables and with online days away, will always be just a little different.