The most realistic racing simulator on PC is widely considered to be Assetto Corsa. It offers a realistic driving experience with realistic physics, excellent sound design, and a variety of tracks and cars. The game also features an advanced AI system that makes it challenging for even the most experienced virtual racers. The game also has modding capabilities, allowing players to customize their racing experience even further. Assetto Corsa is the perfect game for anyone looking for an immersive and realistic racing experience on PC.