Don't dig the black cat. She looks like a GRANDMA. The only thing that's nice is the cleavage and the body but the face is UGLY. Get a different artist to do her face please. Her face ruined the figure.
Stick with the Volume 5 series, beginning with Superman/Batman: Supergirl which reintroduced her and go into Power, continuing on from there. The entire series is 67 issues but it's the best incarnation of Supergirl ever, even including the New 52 Supergirl, which is drastically different.
In the Volume 5 ongoing series, Kara absorbs her ship's artificial sunlight for 25 years in suspended animation, explaining her powers manifesting quickly after arriving on Earth and why she's theoretically more powerful than Superman. Superman actually had to grow into his powers whilst living on Earth and didn't manifest them until puberty.
The Batman Beyond movie actually came last, after the original Batman TAS movies. Of which the original poster missed one, the last one following Season 4, Batman: Mystery of the Batwoman. As well as missing Superman: Brainiac Attacks, so this can't actually be a "best of" forum without counting those two movies as well. Not sure why they were left out as they were DC animated movies just the same. Also, I fixed the titles with correct punctuation so they don't look like a second grader typed them up.