As I've want to do sometimes, I took your regions and ran some searches on WA, the only criteria in the search was the region identified and wines produced that scored over 90, here are the results:
Lodi - 57 total wines
40 Zinfandel
6 Petite Sirah
4 Cab. Sav.
2 Syrah
Sierra Foothills - 1 Total wine
1 Syrah
Sonoma - 3107 Wines
1174 Pinot Noir
339 Zinfandel
248 Cab. Sav
168 Syrah
32 Petite Sirah
4 Sangiovese
3 Barbera
Napa - 2149 total wines
1234 Cab Sav
334 Chardonnay
69 Cab Franc
59 Syrah
41 Petite Sirah
29 Zinfandel
Paso Robles - 561 total wines
59 Syrah
35 Cab Sav
22 Grenache
11 Mourvedre
11 Petite Sirah
1 Barbera
Obviously I didn't list every varietal, just the more numerous and popular varietals. As you can probably see from the list, the location of "premium" grapes depends upon the varietals. If you want Syrah, Sonoma looks to be a good choice of the above areas, Pinot Noir - Sonoma, etc. Of course, these are only WA wines and there are many more rating services, and many more AVA's out there.
Searching by varietal instead and not limiting the AVA's, Barbera for instance, yields the following areas where 90+ wines were produced in the US:
California Central Coast - 10
Colombia Valley - 8
North Coast Cali - 5
For Syrah:
Just an interesting way to play around with the rating services to see if any insight can be gained when you are trying to figure out in which AVA the best bang for your buck may lie for a particular varietal.......