I've done a bunch of them. Solvang Century 9 times. It has the most people of the rides I've done, and has celebrity riders, like the winners of the past RAAM. I rode with Pete Penseyers and his wife, they were on their tandem. I like the Cool Breeze here in Ventura. Good course, good food, not too many squids. Also love the SLOBC rides, Lighthouse and Wildflower. The best food, including chocolate fondue at one stop.
Lately my favorite rides are put on by a local endurance racer and named after him. Tour de Francis rides are invitation only and under 100 riders, always a hard course in the mountains, and have the BEST support of any ride I have done. Last time they would grab your bottle on the steep climb, fill it, then run up and hand it back to you. In December they had a KOM competition with lines on the road at the top of the climbs and trophys and plaques at the end. They wouldn't take any money at one and asked for $5 at the other.