DC has at least one Jewish superhero, a member of the Global Guardians named Seraph.
Not that he has been used a lot, mind you.
A fair number of other characters are also Jewish (The Thing of the FF is the most well-known), but very few make a point of their belief in and/or pratice of Judaism. The story where The Thing is revealed to be Jewish is fairly recent and surprised a lot of folks. There is evidence that he is not particularly spiritual or religious, however (for one thing, he was not chosen by the Goddess in the Infinity Crusade series).
Pre-Crisis, Colossal Boy of the LSH came from a Judaic family. When he married his parents wanted to convince him to raise his sons in the faith.