The very concept of Superman and Batman teaming up is awesome per se.
The second story arc brought Kara Zor-El Supergirl back after nearly twenty years. Since then she has become again a staple of the Superman and DCU mythos.
In Superman/Batman #25, Darkseid sticks Superman on the Source Wall (the edge of the universe). However, Superman is freed by... an army of Supergirls: original Silver Age Kara Zor-El, Power Girl'', Linda Danvers, Cir-El and post-Crisis Kara Zor-El leading them all.