Arrival of Kara
I enjoyed this movie since the Public Enemies was just as good in showing the differences in Batman and Superman. Here this continues as they debate how to deal with Kara Zor-El. Later Darkseid takes an interest in her and attempts to corrupt and turn her against Superman. Kara defeats Darkseid and later takes her place in the DC world as Supergirl.
One key element that made this movie work was the casting of the voice actors. One of my complaints about earlier animated movies was changing the VAs for reasons known only to DC. These movies prove that Kevin Conroy and Tim Daly will probably always be the best for Batman and Superman. Keeping the same VAs goes a long way to keeping the fanbase.
Yes there were changes from the comics but since these are only 1 hour long movies instead of 1 1/2 or even 2, things had to be cut out or changed. Having Superman go all out on the Doomdays was the substitute for not showing the all out against Darkseid. This allowed Supergirl her moment instead of showing her inexperience. As a fan of both Supeman/Batman as well as the Supergirl series, this only was for the animated movies fans and not the serious fans. I'm a firm believer in putting in as much as possible to flesh out the story so yes this could have been a bit longer.
I woudn't mind more Superman/Batman animated movies after All-Star Superman