One thing this thread makes clear is: I need to get out and ride more! I'm inspired by many of the places and trips you folks have listed
Second, I don't really have a favorite, but the top rides are all very special for different reasons. I grew up riding from Texas to Colorado on the back of my dad's GS850 every other summer (my brother got the other years). The ride to Amarillo was always brutal, but after Raton pass it was great. Most memorable was the ride into Ouray, CO in a pouring rain. My dad told me not to move and I felt like I didn't flex a single muscle for 45 minutes. That trip had all the beauty of the Rocky Mountains through Ouray, Silverton, Durango, Craig, and Estes Park. That time with my dad was the best and can't be replicated.
My other favorites are all with my wife. We took the dirtbikes (CRF250x & CRF 150) to Ouray and rode Imogene & Engineer and a few others. She had never ridden before we got together and learned only 2 years before this trip. She rode well and saw things she'd never otherwise have seen. Sharing that with her and seeing her skills rise to the occasion was better than any other off-road experience I've had. On road with her was our honeymoon, an Edelweiss tour of New Zealand (R1150RT). The roads and scenery were amazing and the people were great. We celebrated our 10th Anniversary on an Edelweiss Tour of Tuscany (R1200RT). Great food, roads, and scenery. For the latter, we had the benefit of Bluetooth intercoms which was a game changer.
I'm shooting for a Celtic Rider Ireland tour this summer if a few things fall into place - maybe it will make the favorites list.