Do creatures with enchantments on them keep the enchantments if they return to the battlefield from the graveyard?
No, nothing like that happens. Once the creature is in the graveyard, it's no longer associated with the aura in any way.
When the creature dies, the aura is sent to the graveyard as a state-based action (i.e. the next time a player would gain priority):

704.5n If an Aura is attached to an illegal object or player, or is not attached to an object or player, that Aura is put into its owner’s graveyard.

And the creature card and enchantment card in the graveyard don't know they were ever associated:

400.7. An object that moves from one zone to another becomes a new object with no memory of, or relation to, its previous existence. There are eight exceptions to this rule:
[...exceptions that don't apply here...]

So if you return the creature to the battlefield, it's yet again an entirely new creature, nothing to do with the aura that was once attached to that creature card.