Once I get this game, I want to see how much it owns the Super Robot Taisen series, and I love the SRT series dearly.
There was a trailer that I had of Namco X Capcom, and after watching it, I literally fell in love with it, and the background music they used for that trailer... it'll seriously convince anyone to get it. I know I'm convinced.
Right now, as far as I know, the following series are in the game:
Capcom side:
Rockman Dash/Legends
Strider
Street Fighter (Zero)
Ghouls and Ghost
Dino Crisis (...?!)
Darkstalkers
Captain Commando
Forgotten Worlds
Rival Schools
Namco Side:
Soul Calibur
Druaga
Xenosaga
Tekken
Tales of Destiny
Klonoa
Edit: after watching the current trailer, The background music is similar, but the one I listened to in the other trailer was a piano solo, showing EARLY versions of the game.