If we're going off COMIC BOOKS...
X-Men
Guardians of the Galaxy
Avengers
Fantastic Four
Inhumans
The Runaways
Defenders
Although I enjoyed all of them growing up. | I enjoyed the Runaways more just because they were teenagers and I connected with that more than the Defenders.
And the Defenders always felt like the people they didn't want to add to the Avengers so they just threw into the little brother group. | I think there is a big gap between the movie and comic versions |