"Marvel cartoons (apart from Spider-Man) spent most of this era living in the shadows of DC material and original heroes from the likes of Hanna-Barbera. But the tide would change as the 1980s dawned...."
I'm going to assume you mean the Spider-Man, Spider-Man and his Amazing Friends and Incredible Hulk series (Don't remember if the Iron Man series fell within this time line or not.)
It'll be interesting to see a defense of this point because I'll tell you, in my area and with my group of friends, those shows weren't getting anywhere near the same play that the various Superfriends imprints were getting, especially "The Super Powers Team: Galactic Guardians."
If I'm being 100% honest I don't know that Marvel has ever managed to succeed in outshining DC when it comes to animated shows. During the 90's X-Men and Spider-Man were fine, but I don't remember any of them with the same fondness I have for the Batman/Superman Animated Series or Batman Beyond.
Even through the 00's shows like Teen Titans, Young Justice, Justice League Unlimited and Green Lantern completely outstrip Ultimate Spider-Man, Avengers Assemble or that weird French Anime Fantastic Four mess they produced a few years back.
Spectacular Spider-Man (Literally my favorite incarnation of my favorite Super Hero) and Avengers: Earth's Mightiest Heroes continue to be the only shining light in the murky pool of Marvel's animated mediocrity