Criteria will include such factors as one day rides, overnight rides, local rides and inter-state rides that you would do again.
For me this includes the following:
Ride up Hwy 33 out of Ojai on to Lockwood Valley over to Frazier Park near the 5 freeway. Hwy 33 and also Lockwood Valley Road are not simple roads and offer plenty of challenge if you get tired of Ortega Hwy. Be sure to stay alert through the passes. On two different rides, a rider has taken a spill on this route for one reason or another.
Santiago Canyon Road. This is a very short tour of just over 20 miles but is very close by, and the first road I did in a group of three riders. If you need to go for a short ride this is it. You can stop in at Cook's Corners and meet lots of motorcycle riders. Lost count of the number of times I have been through here.
Trip to Colorado and the San Juan Mountains. As a really long multi-day ride this was a trip of a lifetime that I would do again. So much to see along the way including Monument Valley, Mesa Verde, the San Juan mountains around Durango and more.
Ride to Monterey, CA up Hwy 1 Stan mentioned this one. Up Hwy 101 to the Coast Highway- Route 1 past Hearst Castle, all the way to Monterey. A good technical road with plenty of turns and twists. From Monterey we (Ken and I) went to San Jose and stopped in at the Winchester Mystery House. We missed Alice's Restaurant up in the Redwood Country. A definite target for the next time. Lots of alternate trips in that area and the Redwood Basin is worth a trip.
Watch for more additions.