Wonder Woman Animated Film 2009 - Hot
Planet Hulk
Green Lantern First Flight
Superman Batman Apocalypse - SuperGirl Hot
BATMAN : UNDER THE RED HOOD
Those were all good, esp. Wonder Woman and Batman: UTRH.
If you like that kind of stuff, also try
Batman/Superman movie - world's finest (not bad and the first one in which they start working together)
Superman Batman Public enemies - as good as or even better than Apocalypse
Superman Doomsday
Superman Brainiac attacks
Batman vs Dracula
Justice League: The new frontier
Ultimate Avengers 1 & 2
Hulk vs Thor and Hulk vs Wolverine
and a few more Batman animated movies like 'Mask of the Phantasm', 'Gotham Knight' and 'Mystery of the Batwoman'.
They are all worth a watch.