My personal favorite of the GTA Trilogy, and the remaster I am looking forward to most, GTA San Andreas included many RPG-lite elements that did not even make it into the later games.
Taking control of CJ Johnson of the Grove Street Families, players could conquer territory from enemy gangs by picking up random NPC gang members from the streets of Los Santos, and conducting drive-bys and the like. If you stayed too long in the wrong neighborhood you could be the victim of an attack by an enemy gang yourself.
CJ would get fat if you ate too much, lose weight if you exercised, and gain strength through working out, which would increase melee damage but also go down over time. The range of haircuts, clothes, eating establishments you could gain health at/rob, girlfriends you could date and get in-game bonuses from, and other side quests was much wider than in GTA IV or GTA V.
GTA San Andreas was the first title to include such a large range of radio stations as can be found in GTA IV and GTA V, and (in my opinion) had the best soundtrack of any GTA game so far.
Arguably the best part of the game though was the characters – Ryder, Wu Zi Mu, Catalina (technically also in GTA 3), Mike Toreno, and of course, Big Smoke are some of the best GTA characters in the franchise’s history.