My personal favorite is 1975 Topps. It was the first year I collected cards and it was, IMHO, the most color set of the decade.
My favorite memory of the set is trading Hank Aaron straight up for Dick Allen. The White Sox were my team and I wanted all ChiSox cards. Of course, to my dismay, when I turned the card over I saw that he had been traded to the Atlanta Braves.
The Allen card is still my favorite card from the set.