Why can't I download Final Fantasy on my iPod Touch 4

I previously purchased Final Fantasy (the original) a few years ago, and ended up deleting it after a time.

Today I tried to redownload it, only to find it not in the app store, even though final fantasy 2,3,4,5,6,7 and 4 after years are all in there.

I downloaded it on iTunes on my PC, and it says it can't download it on my ipod touch.

Please help!