Feel free to provide your own details (and source) of who's playable or included in the game.

Also, any wish-list characters?

MK vs DC: The Roster

Mortal Kombat

Jax
Kano (http://kotaku.com/5039348/wonder-woman- … kombatants)
Kitana
Liu Kang
Raiden (http://kotaku.com/5039348/wonder-woman- … kombatants)
Scorpion
Shang Tsung
Sonya Blad
Sub-Zero
Shao Kahn (http://www.mortalkombatonline.com/conte … roster.cds)
Baraka (http://www.mortalkombatonline.com/conte … roster.cds)

DC Universe

Batman
Catwoman
Deathstroke (http://kotaku.com/5039348/wonder-woman- … kombatants)
The Flash
Green Latern
The Joker
Shazam
Superman
Wonder Woman (http://kotaku.com/5039348/wonder-woman- … kombatants)
Darkseid (http://www.mortalkombatonline.com/conte … roster.cds)
Lex Luther (http://www.mortalkombatonline.com/conte … roster.cds)

*13 Sept 09, added four characters: Baraka, Shao Kahn, Darkseid, and Lex Luther