It sure seemed like GTA V was a pretty large technical shift from GTA IV, and even more so for the games before that. Part of the awesome appeal of GTA, for me at least, was the totally stupid shit you could do. The ragdoll physics, the dumb shootouts you would get into, sending yourself flying across the map.
GTA V doesn't necessarily allow for all of that, at least not to the level of previous games. The newer games, while not necessarily being self-serious, don't allow you to do the super dumb shit that you used to be able to do in previous versions.
For that reason, I prefer the old ones for their timeless replay-ability and sandbox-y-ness, but the newer games (specifically GTA V) for their technical ability.