I like to keep every game of the series and the ones related to them (like FFVII sequels and all that),and every versions of the games but i guess i could sell FF Origins and FFVI as i don't have anything to do with it, i rather play the GBA versions.

I also could consider selling VIII for a high price cause i don't see me playing that one again. But i still have everyone in the series except XI.
Crystal Chronicles for GC i have sold and i don't buy the rest of them,Tactics or Dissidia.