Unpopular opinion, and I'm ready for the pushback - I don't think GTA games age very well. In the past year I've tried to play 3 and 4, games that I played to 100% completion when they were current, and I just couldn't play either for more than a few hours. There has been such a tremendous leap between each game, whether it's graphics, gameplay, storytelling, whatever, that the previous games get left in the dust. That having been said, this is going to be a pretty nice payday for Rockstar.
Note: This is interesting: Additionally, all three games have revamped controls, bringing them more in line with GTA 5. Specifically, movement, camera and targeting controls have been overhauled, which should make them more playable than ever.... Also radial menus for weapons, customizable waypoints, and instant mission restart upon failure. So that could definitely be something.