Character you control: Check Minus (you don't get to name him)
Other NPCs to interact with: Check Minus (You only get response choices occasionally)
Each play-through is unique: Check
Ability to roam around on your own and experience the world: Check, Check, Check!
Customization of your character: Check
Gaining skill through experience: Check
Save/Load Feature: Check
Side-Quests Abound: Check
Inventory & Item Acquisition: Check
This compares about evenly to FFX, except in GTA: San Andreas, you get more freedom to roam the world, far more side quests, a more fleshed out world, and a more unique experience every play-through.