The upgrades will include "additional features such as multiplayer simultaneous play," which is kind of a big claim, since not even the Game Boy Virtual Console games sold now have multiplayer functionality. Nintendo didn't detail any other changes, except to say that 3D isn't one of them. The games won't be remade as 3D Classics.
The list of NES games announced includes Super Mario Bros., Donkey Kong Jr., Balloon Fight, Ice Climber, and The Legend of Zelda. These and five more unknown games will be included in the Ambassador Program. Ten Game Boy Advance games will follow later in 2011.