I agree there is a great power & influenced that fans have if not sometimes being an influencing factor to possibly executives, writers, and artists then towards the general public by how we possibly advertise 'characters' from: forum topics, general conversations, social media posts, and fan arts/works.
We are ambassadors of '616 MJ' and other characters we might be fans of (sometimes good or bad). Though we are also individuals influenced by various factors and have a great possibly to have different viewpoint and ideas to the very same character version we are a fan of.
But if you look to WHO(S)/WHAT(S) made it possible for 'fans' to care about any versions of any characters? Fans don't come from a blank void. Something has to make you a 'fan'. There are people who work to make you a 'fan' or made something that by chance just captured you and others. Writers, various artists from Designers, penciler, inker, colors, panel and tone planning, ect and even a bit of Marketers somehow found and able to create a fascination to draw us in and hold us somehow.
Writers and Artists also can be part of the 'fans' category as well for many characters. They as well were/is influenced by stories/works from others or other many various ways inspirations can come about that spark new ideas & hard work from them.
Before any 'fans' exist their has to be a writer(s) and artist(s) that brings life & possibilities/interests from characters. Something maybe small or large that gives birth to 'fans' of characters. Writers and artists work very hard in their craft hoping to tell stories that not just we would hopefully enjoy but they want to make (sometimes they might be forced not by desire but by executives, time, and other matters outside of their control yet even so they try their best still for positive craftsmanship & outcomes). Writing and designing characters born from imagination that was sparked by anything from life experiences, a small moment in time, other art, cultures, small talk, ect.
Every character unless the creators desired for a character to be hated (not 'love seeing them be vile' but actual hate hate) or people to feel neutral towards is designed to capture us and have some sort of 1st purpose/role that hopefully evolves the story, developments, tones, and more of themselves and/or other characters and plot plus possibly the target market readers and maybe for new readers. In time new ideas from the same creators or other allowed to use such characters somehow continue to expand their possibilities or towards the other directions.
No question in looking to the history of comics and characters for certain time periods with the focus the time both was being crafted fictional character 616 MJ was more popular then fictional character 616 Gwen even if that may or may not been the desired intent from some creators (all art is subjective thus even if a writer and artist might aim for intent to one direction they are hoping for it can curve to any direction from others sometimes). Still writers and artists are the one's that have powers they earned by hard work to create and give influences (intentional or not) both positives and negatives to any character.
Some building off from each other while others move in different directions then what previous creators might of intended and we all hope in history it will be positively viewed somehow.