The only thing I have against GTA V is that cars can't be saved in story mode. I hate paying 100,000+ upgrading a car, just for it to disappear after a mission is started.

If you go far enough in the story, each main character can buy a warehouse to store cars in. The DLC that adds cars gives you the warehouse up front since it stores them there.

Yes, I've had the game completed for some time now. But still, cars that are bought aren't saved - unless parked in a garage/safehouse.