Spider-Man and His Amazing Friends only lasted a measely 24 episodes, but it was certainly my first meaningful exposure to the Marvel Universe. There's a certain cheese element to it now, but to a 9-year-old this was super-hero gold.
More importantly, this is where I was exposed to the X-Men for the first time. I remember when I first saw the "A Firestar is Born" episode during Saturday morning cartoons, and immediately called my cousin too see if he saw it too.
This episode had it all -- an origin, Juggernaught, Angel, Cyclops, Wolverine, Professor X, Storm, and a distinct lack of Ms. Lion the dog. Keep in mind that this episode was first aired in 1982... a full seven years before we would get an actual X-Men cartoon of any kind.
Wolverine might not have had the best voice in this episode, but for months afterwards my cousins and I would constantly shout "It's my turn!"
Let's take a look at the last 7 minutes of A Firestar is Born: