I have no idea how well it holds up after all these years, but it was Stan Lee's original "Infinity" saga (along with the first Kree-Skrull War) that originally hooked me on Marvel Comics.
(Not to be confused with all the stuff with Thanos and the Infinity Gauntlet decades later. This was a twelve-part storyline back around 1970-1971 that had Thor battling a mysterious entity known only as "Infinity." I ate it up when I was in junior high.)