I find rankings games which span across four generations to be honestly very difficult, due to them being so different and them all having their own pros & cons.
1.IV + Episodes From LC, I think all three games compliment each other & make each other better so rightly or wrongly I view them as one game, and the IV saga would be my personal favourite.
2.III, It's this high simply for its unparalleled atmosphere & the fact it was the GTA that made me fall in the love with the series, so I'm slightly biased when it comes to III
3.V, the game is simply a technical marvel with one of the best-written scripts I have ever seen in a video game, I have also played it more than any other GTA when it comes to hours.
4.LCS, for its memorable & hilarious characters & mafioso mob narrative
5.GTA 2...just a classic.
I always thought the story in San Andreas was horrible & the game's content was mostly gimmicky, overrated, & not needed so I've never been the biggest fan though I do respect the game.
Vice City has always been a mixed bag to me I love the games 80s vibe & soundtrack, but I hate Tommy & Vice City is a poorly designed city, also the narrative is highly predictable and the characters are just meh.