I didn't techinically buy all the versions of FFIV but I do/have own(ed) them all:

-Borrowed the original SNES game from my brother's friend
-Bought my own copy (or my brother did, one of us did)
-Bought FF Chronicles version for PS1
-Own the DS remake
-Own the PSP FFIV: Complete Collection

How about Tetris:

-Bought the original NES game
-The Game Boy version came with my Game Boy
-Lost my Game Boy so bought a new one, which came with another Tetris (so I had 2)
-Does buying Tetris 2 count? It's basically the same game
-I'm sure I downloaded a Tetris rom at some point
-Own Tetris DS, both the actual game and the rom
-I think I have the Tetris cell phone ap, if not I will get it now