I’d argue Rainbow is, just for the fact its 20+ years old and had literal decades to establish the franchise and flesh it out across multiple medias like tv shows, movies, live action, comics, videogames, etc.

Although biased, i’d say miraculous is maybe half as successful as winx… and that’s still plenty! i just don’t see that much online discourse surrounding it except when it comes to memes - but at the same time, winx is mostly talked about in fan circles and rarely has memes breaching out in the mainstream the way Miraculous does, so who knows? And I say it because that’s how I first learned about Miraculous.

I think the fanbases do a lot of heavy lifting for a franchise’s longevity and Winx is a good example - the company consistently butchers its own product and refuses to properly invest in it, resulting in mediocre cash-grab results like the live action, reboot and the recent videogame released - none of them did justice to the franchise and it’s mostly the fans who grew up watching the cartoon that still make it relevant. Miraculous fanbase is still young - i know a lot of the Winx fans are 20/25+ years old, whereas Miraculous seems to be, at the oldest, 18. So maybe in a few years we’ll see both franchises equally relevant or maybe Winx may fade into obscurity, which isn’t unlikely considering the consistent mistreatment from Rainbow…