Mr. Silver Age in CBG always lists Flash # 167 as the worst D.C. story ever ( it has one of the greatest "grey wash" covers you'll ever see, tho)!

I never cared for the post-67 Infantino-Giordano line retooling because all the flagship titles slipped in quality at the same time.
I'll take 1965 D.C. as the company's zenith, and each year thereafter saw a dropoff.
I'd say Marvel equalled D.C. in 1966, surpassed it in '67-69, and both companies were even again from 1970 onward.