I voted for DC, which was the dominant company distributed to my town's local drugstore during my elementary school days in the '50s. ACG was my second favorite, although I had to ride my bike across town to a little family grocery to buy them. I also saw Dell and Harvey comics, but DC was pretty much the main player available. My brother and I mocked the ridiculous Mort Weisinger Superman universe (with Bizarro Superman, Superboy, Jimmy Olson, Lois Lane, and so on), but it was the only game in town.
During my junior high and high school years, Marvel got back into the superhero business and with my family moving to another state, suddenly Marvel was being distributed to the local shops. I mainly switched from DC to Marvel during the '60s. (Gold Key also won me over in this period.) However, by the time I left for college in '68, I was mostly done with newsstand comics and shifted my attention to underground comix and the underground press. It took GAC and DCM to pull me back into appreciating the Golden Age comics that I'd mostly missed because they were all before my time.
Happy Halloween to everyone here and thanks to Michael T. Gilbert for a great Halloween DCM animated logo GIF.