Has no one been to Santa Cruz Beach Boardwalk? Giant Dipper should certainly rank up there, as well as the Giant Dipper at Belmont Park in San Diego, which still rocks. And Joker at SFDK should be up there as well. One person mentioned Deja Vu, but that hasn't be in CA for years, so I don't think that should count. Same goes for Green Lantern: First Flight... which, good lord, how did that get to #4? While I didn't hate it as much as most did, even I would've never put it up there, lol.
Being a local, I really value reridability. X2 is a lot of fun, but it's also pretty rough, so it would go much lower on my list, while Superman, while admittedly not as thrilling or intense, is much easier and very fun to reride, so I'd put it higher on my list. More family coaster appear on my list for this reason as well... some of the more thrilling/intense rides can really bang you up, so they'd be lower on my list or not appear at all.
It's tricky, as many others have mentioned, SFMM kind of dominates the CA market in terms of roller coasters. If I took SFMM off the list, I'd say:
Excluding SFMM:
1. Ghostrider, KBF
2. Xcelerator, KFB
3. Giant Dipper, Belmont Park
4. Railblazer, CGA
5. Joker, SFDK
6. Giant Dipper, SCBB
7. The Flash: Vertical Velocity, SFDK (I'm a sucker for it's unique variation)
8. Manta, Sea World
9. Space Mountain, DL
10. Big Thunder Mountain Railroad, DL
Including SFMM:
1. Ghostrider, KFB
2. Twisted Colossus, SFMM
3. Superman: The Escape, SFMM
4. Giant Dipper, Belmont Park
5. Xcelerator, KFB
6. Goliath, SFMM
7. Railblazer, SFDK
8. West Coast Racers, SFMM (again, mainly because it's fun and very reridable)
9. Apocolypse, SFMM (since the retracking, it's actually in pretty good shape)
10. Giant Dipper, SCBB
Honorable mentions: Quicksilver Express at Gilroy Gardens (very mild and a bit wonky, but endearing somehow), Goldstriker at CGA (love it's layout, but it's gotten really rough over the years), Medusa at SFSK, Montezuma's Revenge at KFB, and The New Revolution at SFMM.
I'm also surprised so many wooden coasters appear on my list, as I generally think of myself as more of a steel guy. But the good woodies we have out here are really good.