Originally Posted by Bimmer Loyalist
If you're into realism it's a must. My first driving sim was Gran Turismo 3 which is subpar at best (highly overrated). Gran Turismo 4 is simply GT3 with eyecandy (again, overrated).
Forza's main focus is real-world vehicular physics. Everything is actively monitored from suspension travel, tire temperature, lateral grip, lateral g's, weight transfer, and much more. It makes GT feel like an arcade game in comparison.
The one drawback is that the game's graphics are way below par in relative to the competition. It's a result of a compromise made for a consistent 60fps and realistic crash damage. Worth it to an extent in my opinion.
Sounds good, I'll have to check it out. My first realistic driving sim was GT3 as well, was the most entertaining game I think I have ever played.