I discovered sports in a big way when I was 9, so 1975. UCLA basketball because John Wooden was going to retire so they were sort of the great story, Warriors NBA basketball the local team, and Cardinals in football(and baseball) presumably because I was born in Missouri but grew up in Cupertino, CA.
Terry Metcalf was my favorite Cardinal, great player so exciting when he got the ball. That was a great offense with him, Otis, Jim Hart, Mel Gray, a great OL. The defense had no talent because Bidwill Sr wouldn't spend the money.
1975 UCLA won the title and then went 20 years before winning again(and not since). Warriors won the title(Rick Barry) and then went 40 years without another (thank you Steph), Cards were in the playoffs and not long after became terrible for decades with one brief run when Lomax was the QB(very brief) where we were good(but still didn't make the playoffs).
9 year old me had no idea how unusual it was to have all your favorite teams be good at the same time.