I'm not going to lie, I think they are decent finishing moves. Raiden's is pretty cool, and seems like his same old fatality updated. I would not be surprised to see an updated version of all the MK characters fatalities. It's easier and doesn't require much thought, so it definitely sounds like something they would do. I really wouldn't mind to see Liu Kang turn into a dragon again.
As for the Green Lantern, I don't know about you guys, but to me it definitely looks like that "Heroic Brutality" would murder an opponent. The bubble closes up and folds the player up breaking his bones...
The flash's is pretty weak. It looks just like a regular move.
One more thing, I noticed their eyes aren't glowing like in previous videos which is good... and does anyone else think that the on screen text is kind of tacky? RAGE, Heroic Brutality, and Fatality seem to have a weird look.
I don't mind the text style but I think "Heroic Brutality" sounds very lame. I wonder if DC asked for it to seperate their hero characters from the rest, so they appear better/less evil if you follow me.