Personally, I love the Spider-Man TAS the most. It had good voice acting, some of the best storytelling (Clone saga, The Alien costume arc, The Night of The Lizard etc.), nice character designs (especially on Peter), really good drama, and appearances of other Marvel characters :D

My personal favourite is the Avengers: EMH.

The 90's spiderman animated series is my favorite. And is easily the best spiderman animation.

Avengers Earth's Mightiest Heroes

Batman TAS

JLU

Static Shock

I'm not 100% on all the rules here yet so I didn't add any dc but if I can batman tas is top

Spectacular Spider Man was my favorite Spider Man

but the best superhero cartoon has to be JLU and Young Justice

for solo superhero shows Batman TAS

From marvel 60's Spiderman lol

@amazingspiderman15 said:

This

The Avengers: Earth's Mightiest Heroes is probably one of the best ones I've seen, if not the best.

I didn't think it started very strong, and it took me some time to get used to the voice acting (mostly Iron Man and Wasp), but as the series went on I thought the stories got better and better. The character art was kind of overly stylized for my taste, but the action and expressions were pretty smooth and the backgrounds get more and more pleasing as the series goes. Just a solid series that not only did justice to the source material, but seemed to be in a perpetual state of improvement itself.

I remember enjoying the 90s Spider-Man and X-Men cartoons as I was growing up, but I haven't watched either of them going on 18 years or so probably. I netflixed the Avengers EMH series a few months ago and was impressed. It was a very good show.