Only newer title in the series that I've played that I didn't think was complete garbage was Undercover.
It gives you the customization of Carbon with physics similar to/better than Most Wanted. Story isn't too bad either. Plus you get classic muscle cars. <-Winning.
My credentials: I've played High Stakes, Underground 2, Most Wanted, Carbon, Pro Street, Undercover, Hot Pursuit, and The Run.
Out of all of those, I'd choose Undercover in a heartbeat. It's the best of the best so far.
Only flaws: LOLcops and rubberband AI. Doesn't matter if you've got a Zonda and are topping out at 250+ MPH. The Feds will catch up. Same with NPC AI on harder difficulties.
Well, if you don't mind stepping into the realm of Simulation Racing, I'd recommend Forza 2.
Lots of customization, lots of cars. And it has "how to drive simulators for dummies" settings.
I've not tried Forza 3. It could be just as good.
I had a beautiful Nissan z300 in that game. Green with black racing stripes and gunmetal rims. With all the upgrades I sank into that car, it was classified as an 'S-class' racer. I couldn't keep that thing on the track when I floored the pedal out of the corners. Had to gradually apply gas or I'd find myself in the wall. :laugh:
The pacing is really good too. Not like Gran Tourismo, where it takes forever to unlock new stuff.
I honestly don't think the game you want has been made yet.
The closest thing I can think of would be <strike>Motostorm: Apocalypse.</strike> No I take that back.
What you want is Burnout Paradise. Open world, lots of cars and mayhem. Similar arcade driving physics. Customization is limited to paint color, sadly. But that would be the closest thing to what you are asking for.
The only thing that bugged me about it was a lack of story.
Need for speed: SHIFT is pretty fun. It is a different turn for the NFS series but the cars are pretty quick like the Zonda and there is a large selection of them.
Best racing game I've played though is Dirt 2 though. Lots of fun with a wheel:)
Also GRID and Blur?
But none of those are open world. NFS world is not too bad but the progression can be a bit grindy.
