SA is definitely the most unrealistic in that regard by GTA standards. All Truth missions, Woozie's racing, chasing OG Loc in a cart formula, jetpack etc..
Guess they just wanted to throw in a little bit of everything in that game.
To everyone else, it's not about ''real life realistic'', but GTA realistic. Sure, since it's a game you get much more enemies to fight, but things that we generally do in GTA are realistic things, robbing a bank, stealing a car, killing for money, gang wars, mob assassinations, racing etc are all real life things, the difference being that in real life at most a few people get shot while in games we get dozens of enemies, and can take dozens of bullets so that it interesting to play. But some of SA missions are far away from reality, while GTA games are usually grounded in reality.