I don't think it's helpful to start labelling heroes, A, B, or C list ect.

As far as the traditional JLA members go, he would most likely be in the Atom/Firestorm/Zatanna range somewhere, but more popular or significant than Red Tornado or Phantom Stranger.

-Traditionally he has been a key member of the Teen Titans since the 80's (that's his comic claim to fame)

-An on off member of the Justice League dating back to his appearances on the Superpowers cartoon & comic (80's again)

-He has had at least one solo series that I am aware of. About 5 years ago, I believe it lasted two years.

-Finally, he has had notable appearances on DC animated movies, and video games if I am not mistaken. (Going off my head
here)