I notice the big six of Marvel basically fit with DC's big six as being made to be 'solo heroes' - getting their own solo book, their own supporting civilian cast and themed ally heroes and rogues' galleries, and in 2/3rds of the members helping found the "premier" hero team of their world. You could nominally say, commission their own set of movies, a cartoon, etc. and fill it out with just 'their' stuff from the comics without nominally grabbing filler clearly connected to other heroes or the universe in general. It's not a perfect 1-to-1 comparison. In general, Marvel characters are obviously far more interconnected than DC's tend to be. Spidey never helped found the Avengers even if I argue his now longtime status as one helped both him and the team get new growth and prestige, and Wolverine *ultimately* feels he belongs as the star member of the X-Men than part of the Avengers' world and an ensemble guy in general than a 'solo hero', even if he technically fits the 'solo hero' criteria above far more than any other mutant.
If I truly had to distill Marvel to its 'core' heroes it'd be the six founding comic Avengers (Cap, Iron Man, Thor, Hulk, Ant-Man, Wasp) and Spider-Man with them, the Fantastic Four, and all-new all-different X-Men (Wolverine, Cyclops, Storm, Jean Grey, Colossus, Nightcrawler) with Beast and Iceman due to Beast's prominence in Avengers and Iceman in Champions and their worldbuilding connections. DC's 'core' to me are the big six solo book founders of the JL, the New Teen Titans sans Wonder Girl (keep Wally, he's vital to Flash mythos), and a couple connected characters to the big six (Babs to Batman, Supergirl to Superman, John Stewart to Hal Jordan, Mera to Aquaman). These two distilled 'core' hero lists are to me the best balance between A-list from media adaptions and being A-list in-universe of the comic continuities.