I think people call GT3 realistic mainly because controlling the cars is a b*tch compared to most other racing games. For example, the cars actually have momentum, so you tend to oversteer massively when you first play the game. GT3 might not have simulator-quality realism, but it's more realistic than most racing games people play (ie mariokart).

-Adam

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"It's not that I'm lazy, it's that I just don't care..." -office space