The first Grand Theft Auto game I ever played was Grand Theft Auto III, and I think it’s the only GTA game that I never actually completed. I was something like 9 years old at the time, and I just didn’t have the attention span to go through every single level and play the game to completion.
That being said, I completed every GTA game afterwards, including the incredibly long and boring GTA V. I can’t say that I 100% completed them (I mean, who has time for all those collectibles and stunt jumps?) but I completed the main/side stories at least.