I know the top five climbs I would climb again, in a minute, if I could (although most would take about 85 minutes): Col du Galibier, Col du Tourmalet, Col d'Aubisque, Col de la Marie Blanque, Mont Ventoux. In the United States I'd ride Trail Ridge Road in Rocky Mountain National Park (both sides) and Cottonwood Pass near Crested Butte, Colorado.
5 rides in Europe
Passo dello Stelvio, Alps, Italy
and in Ireland Healy Pass, Co.Cork, Ireland
or, 5 rides in the United States
Independence Pass, Aspen, Colorado, both sides in the same day