Hello people! So I saw there is no free, good emulator for the 2600 in the play store, but I searched the internet and found ataroid. The first link found via google here (can't link to a site hosting roms *directly*, can I? "XD") https://www.google.nl/?gfe_rd=cr&ei=n0kBVpyNJoGx8weL9py4DQ#q=ataroid
Just install the apk you extract from the archive, et voila, a perfectly functional great atari 2600 emulator on your XD or Q9 or whatever. It works great and is really easy to use. On the XD (and I assume the Q9 too), after you configure the physical controls in the menu, select button cycles the game modes on the "cartridge" and start button starts, or resets, the game like on a real atari 2600. Dpad for movement and a button for shooting works great for games like space invaders and such.