JLU was great. Haven't seen Young Justice, but I'm acquiring the new GL cartoon from parts unknown and really like it.
There are a BUNCH of Marvel cartoons on the go right now or recently if you include those Japanese ones. You could probably have an entire Superhero cartoon channel on Sky if you wanted.
My favourite Superhero cartoon is probably the 90s X-Men one, or maybe Batman TAS from around the same time.
Just legendary. I never imagined it could get to that level. Blatantly making superhero cartoons for adults and getting the kids along for the ride.
The Legion of Doom/Cadmus saga was epic. Making "For the Man Who Has Everything" perfect... priceless.