There have been times where I've thought about it, but then it feels like I'm making a chore for myself.
For me, I got to 100% in only III, VC, and SA....With the help of a friend, back in 2007, as to me, it also would of been a chore and really frustrating. But once I learned of all the proof vehicles in these games back in March of 2014, I thought of re-doing these games and not only reaching 100%, but also having 0 deaths, 0 busted, 0 cheats, 0 missions failed. I never used cheats before, but I did have some deaths and busted in my past saves, and also missions failed and also not nearly enough proof vehicles as I thought existed.
So in April 2014, I started SA again. After all those years of not playing it and actually dreading to do 100% again, I realized once I started the game, that I forgot EVERYTHING. So SA was as fresh as GTA VI would be, tbh, completely new and not knowing anything about it. Once I obtained the first proof vehicle on my list to obtain in SA, that is when the game became more serious to me and gave me the fuel I needed to complete and gather up as many vehicles as I could, thus not having the feeling of the games being a chore. After I finished SA with 23 proof vehicles, 100% Completion, 0 Cheats, 0 Busted, 3 Deaths (Had to die to obtain 3 vehicles) and all missions passed without saving over a failure (unless it was required to obtain a vehicle), I then felt extremely proud of myself as I did NOT need help from a friend and I did it all by myself way better than most people can do in SA. This once again gave me the fuel to then do GTA III 2 days after I finished SA, and in this game I was dreading it even MORE than SA as it's the hardest in the series by far. Nobody will reach 100% without cheats unless they carefully plan this game and also are determined as it's really f*cking hard, not the story, I mean tasks in general to reach 100%. Again, once I got all proof vehicles in the game, 100%, 0 cheats, deaths, busted, missions failed, etc, I did VC and did the same thing, then LCS, and VCS and did the same thing. I got extremely good saves with amazing collections and after trucking through all 5 games back to back to back to back to back, SA is still my favorite game.
So no, it's not nastalgia (as I forgot EVERYTHING from 2007 when I did the game the first time) or a fetish with CJ and all this "SA fanboy" nonsense like people keep claiming as to why me, and millions of others like SA, it's simply cuz SA is a great game and has tons of memories and things to offer. Out of all 5 3D Games, I felt SA was the most memorable cuz it was the most varied. It didn't actually feel like a chore. Whereas LCS and VCS felt more like a chore than any of the games, but SA is farthest from the chore due to it's variation which was essentially a breath of fresh air.
So all in all, SA is always gonna be by far the best game for me with the most variation and fun in a GTA game hands down. But overall, I still love the entire 3D Era for different reasons over HD. I rather do Paramedics Level 12, than go Bowling in GTA IV. I rather do Vigilante Level 12, than playing Pool in TLaD. I rather do Fire Truck Level 12, than playing Darts in TBoGT, etc. The side activities for 100% in the HD Era are really silly and Yoga in GTA V ought to the worst one out of them all, however...Since it IS required for 100%, I force myself to do it. If something feels like a chore, I always force myself to do it, knowing that it'll be over in no time. 100 Taxi Fares for instance is a chore, but it only takes like an hour and a half or 2 hours tops. Out of a whole 24 hour day, taking 2 hours to complete a chore isn't something that bothers me...