Daniel had a special freezing enchantment on him so that he wouldn’t decompose. Graham wouldn’t have that same enchantment because there was no magic in Storybrooke at the time. Daniel was in pain because he didn’t truly belong in this world anymore…would you really want to see a decomposing Graham that was in constant pain? Let him go and listen to Daniel…”love again”. However, we can still see the real Graham in flashbacks to old Enchanted Forest or pre Emma Storybrooke. It would be better that way. I want Graham as he was not as a unhappy corpse. 🙂