Why can't the Samsung DVD-N2000 or Toshiba SD2300 play downloadable games?
These two DVD players do not have the required firmware to load the NUON.CD files that the downloadable NUON games come in. The NUON.CD file format was originally created as a means of allowing firmware upgrades to be loaded via CD. A file size limit of 4.5MB was implemented to prevent software piracy on CD format, but a work-around was released to allow larger files to be loaded at runtime, making games like Doom possible as a downloadable/burnable game. In addition, the drives on these players were not designed to read CD-R format in the first place.
As a side note, while the RCA DRC300N will not play commercially released NUON software, it will load NUON.CD files, so homebrew games do work on it to a certain extent. Of course, since this machine doesn't have controller ports (as with the Samsung DVD-N505), the remote control is the only means of playing the games.
The Samsung DVD-N501 (US) or the DVD-N504 (Europe) are recommended if you are looking to download and burn games or apps.