If you're in your mid-20s right now, you probably remember the 1990s Jim Lee-design-inspired X-Men animated series, which ran from 1992-1997. If you're younger, you probably grew up with either X-Men: Evolution or the very-recent Wolverine and the X-Men. However, there is one series that predates all of these.
It was a failed pilot from 1989 called Pryde of the X-Men. I still remember sitting on my mother's boyfriend's couch, ten years old and confused as hell as to what I was watching and why it looked absolutely nothing like the TV series I caught, by hook or by crook, every Saturday morning.
Fortunately, someone uploaded the entire pilot to YouTube. For some reason, they saw it fit to give Wolverine has an Australian accent. Meanwhile, if the character designs seem familiar, that is because they were used by Konami for their 1992 X-Men video game, which has just seen a re-release on XBLA.