I think "epic battles" for most comics fans is epitomized in the Lee/Kirby FF run, such as the first Thing vs. the Hulk story (FF 12, March 1963 and FF 25, April 1964), or the first Avengers vs FF (FF 27, May 1964), and X-Men vs. FF (FF 28, July 1964), all in a row.
And of course the first story with the FF and Galactus, with the Silver Surfer (FF 48-50, March-May 1966).
But for me, even more of an epic battle was the FF vs Doctor Doom in FF 57-60 (Dec 1966-March 1967), where Doctor Doom traps the Silver Surfer and steals his powers, and with that added power he has the capacity to destroy the earth, and stack up some visually striking panoramas of destruction before the FF finally seizes the day. For me the visuals made it convincing, that Doom could actually destroy the world. And at the very least, was visually striking, and cool reading. I first read them in a 1972 reprint titled MARVEL TRIPLE ACTION.
I first read most of these reprinted in MARVEL'S GREATEST COMICS in the early 1970's. Some of them I didn't get to see until they were reprinted in Marvel Masterworks hardcovers. With Masterworks, it was great to finally have the complete Lee/Kirby and Lee/Ditko runs of all the early titles the 1970's Marvel books were founded on and frequently referred to.
The 70's reprints would often frustratingly delete one or more pages, so you got the feel of the original, without having the whole thing.
That was also true of reprint comics like X-MEN CLASSICS in the mid/late 1980's. More than DC, Marvel had more of a tendency to slice and dice their reprints than DC. Up until the Masterworks hardcovers, that is.
