In the sense that Darth Vader was the protagonist and connecting thread of the PT and the OT aka George Lucas' Star Wars. That RDJ's Tony Stark is the Protagonist of the MCU (at least until Endgame). In Ultimate Marvel, everything was centered around Nick Fury. It was always about him, his secret plans, him being connected in some way and some form, to everything in that world.
616 Marvel can't really be said to have a protagonist anymore owing to how big and wide it has grown over the years. Obviously in the classic Marvel era of the '60s, the Fantastic Four were the clear protagonists since the new timeline started with their rocket flight and a lot of the aspects of the worldbuilding were tied to them or introduced through them, and new titles and characters somehow became adjacent to them (like Spider-Man). But that ended when they stopped being the top title and when the X-Men became the top team. You can also make a case that Captain America is also the protagonist, the biggest character in the classic Timely era and him being sent into ice and retrieved is another major watershed moment in the continuity but even then that can be argued and it's not entirely definite.
Nobody just takes the author at their word, you know. Just because Millar makes a self-aggrandizing preening comment in the pages of his own comic, that does not mean anyone has to validate that.
Lee-Kirby introduced Pietro in a title (Uncanny X-Men) that was failing in sales and fan appeal. So obviously their conception of Quicksilver never quite caught on or take for very long. Quicksilver changed significantly after that under Roy Thomas and later writers, he got married to an Inhuman and everything, and became a father.Pietro has ALWAYS been, since Stan Lee and Jack Kirby created him, an overprotective zealot in everything related to his sister.
1) He was never intended to be a serial killing mass murdering cannibal. To the extent Hulk was intended to be a monster, it was in the small-m sense, in the Romantic sense, where you are supposed to be sympathetic and also root for the guy, like with Boris Karloff's Frankenstein. In the '60s Hulk was a counter-culture icon for campus kids because obviously a story of a green giant fighting and tearing up US Military was quite cathartic in the anti-Vietnam War protest era.Hulk has always been supposed to be a monster
2) The original conception of Hulk failed because the miniseries got cancelled after a few issues. So obviously they had to change and redo the character to make him work as a serial successful character.
Saying stuff like "always supposed to be" and citing some factoid about the Lee-Kirby while ignoring the context...and all for the sake of defending Ultimate Marvel is bad faith. Lee and Kirby intended first of all for all their characters and ideas to do well and prosper and both of them understood that if any title they did didn't work, it was up to later writers to come in and do what they figure is right (even if it means overturning their stuff) to make that work.
The Xavier-Magneto dichotomy was created by Chris Claremont and never part of Lee-Kirby's concept, and for it to work, Magneto has to have some kind of legitimacy, some compelling meaningful background and legitimate virtues and strength of character that makes people flock to him and makes him a rival ideology to Xavier. Ultimate Magneto has none of those things and is not a very good villain. As far as characterization goes, even Ultimate Norman Osborn is better than him.As for Magneto, the Xavier / Magneto dichotomy really only works if Magneto is the VILLAIN, not if the Brotherhood is just a secondary X-Men team.