For your Money PGR3 is the best value, it will take a long time to get bored of (if you like racing games) how do you go wrong:
Graphics - Great to impress the ladies with, my mom thinks it looks great
Controls - I've always loved how the cars in PGR handled
Single Player - Varried Modes, Lots of Cars, amazing tracks that are fun to race and look at. Make your own circuit, listen to your own Music (even during load times!) [Even though this is a feature in all 360 games it's most important in racing and snowboarding/skateboarding games imo] etc.
Multiplayer - Wow, very fun, find a good room and get stuck there driving the rest of your night away. Very entertaining. Enough modes to keep you sane. If you get pissed off when you get rubbed out turn off contact, if you like to rough it up... try to survive that first corner
Lasting appeal - Love you Long Time!
Kameo: Cool neat game, worth playing through and only worth a purchase if you can afford it over pgr3.
Condemned: See Kameo