A better question would be is any sim that realistic, and in this case how close to reality is "realistic"? The real world has behaviors that go down to the molecular level, which is beyond what a PC based racing game could hope to model, so compromises have to be made.
In addition, there's the driver experience, since there's no feel of the acceleration forces, it's never going to be the same as real life. Visually exaggerating the roll and pitch responses would help here, but I've only seen this done in a "budget" racing game, Ford Racing 2.
Even in the case of a remote control setup for a real car, it's my belief that lap times would be faster with an external view than an internal view, because it would be easier to judge speeds, the cars reaction, and the cars position on the track, from an external view. An onboard view would be cool, but standing at a fixed position with a good view of the track, or a "chase" view behind the cars direction of travel (one not affected by the cars yaw reaction), would produce better lap times.