If you didn't experience it in the '90s, it's going to be hard to explain the sheer impact of that show at the time. They had been trying to bring X-Men out of the comic shops and into the mainstream for a little while with tepid results. There was an arcade machine, a failed TV pilot and an anemically selling action figure line. That, and the usual mainstream scuttlebutt about how selling a copy of X-Men #1 might make you a millionaire (it was the '90s after all). After the show premiered, that all changed. X-Men was a household name. Those lame action figures flew off the shelves. Trading cards got printed. They made band-aids with Wolverine on them. It was even the goodwill from the show that got the movies off the ground. And though you may think it's "cringe" now, the reason it gained that kind of popularity is that the people making the show fought hard to make the show as dramatic, grown-up and hard-hitting as they could given the circumstances (no lie, they had to fight against making it a comedy show where Prof. X, Cyclops and a dog go driving around in a van looking for mutants like it was some kind of mutant Scooby-Doo). And comparing it to Batman does nothing to diminish that effect, because kids watched both on Saturday mornings. They complemented each other like bacon and eggs. Batman was DC. It had an orchestral theme. It had rounder, smoother animation. X-Men was Marvel. It had a rockin' electric guitar theme. It had jerkier animation but often of crazy detailed visuals. And while both mixed stuff from the past and present, Batman leaned more toward the classic (they were, after all, still playing up Dick Grayson in what had become a Tim Drake world) while X-Men with its character choices and Jim Lee designs at least looked and felt more like what they were putting in contemporary comics that kids could buy.
And you'll probably say "Well, this is all just nostalgia from someone who watched it growing up". And yeah, that's kind of true.
But also . . . it created a baseline. It created a baseline for what the mainstream people should expect from the X-Men. The movies? HA! The movies are some black and chrome, Matrix-era, desaturated take on the cartoon that didn't do the Phoenix right and didn't really use Gambit or Jubilee. X-Men Evolution? The cartoon crossed with Saved by the Bell. Wolverine and the X-Men? The cartoon but more serialized and for some reason that blonde lady from Dark Phoenix Saga is hanging around with the good guys now. It doesn't matter who does it better. After all, it's expected that storytelling will get better and more sophisticated over time. What matters is what gets the concept stuck in people's minds. And this is especially going to be important to remember with Marvel Studios going forward. Because with their needing to essentially relaunch the X-Men for the mainstream and as the comics have kind of become mutations of mutations as different writers have introduced different weird, experimental status quos to play around with, they're going to need a solid baseline to start with or go back to.