San Francisco is, according to AARP, the best big city for older Americans (over 50, I think) even though its score is only 66 over 100.  It scored high 84/100 in the health category (not much smoking but access to exercise opportunities and enough health care professionals) and it got 75/100 for transportation, which includes household transportation costs, frequency of local transit, walkability scores, and ADA-accessible transit stations and vehicles.