Final Fantasy 1,2,4,5 are out for GBA.
Final Fantasy 6 english version will come soon to GBA.
Final Fantasy 3 is out for DS.
Final fantasy 10, 11, 12 are out for PS2. FFXI is also available for XBOX 360 (i think) and PC.
Final fantasy 7, 8, 9 are out on PS1 (also playable on PS2 machine. Use memory card for PS1 to save) Final fantasy 7 and 8 are available for PC as well.
Final fantasy Crystal Chronicle is available on Gamecube.
That's all for the english version of Final Fantasy games. (not counting the ones released on SNES or titled such as Final fantasy mystic quest and other title bearing Final Fantasy name)