Epic Games has updated its store refund policy to bring it in line with Steam's "for any reason" refund policy: If you bought it from the Epic Store, you can claim a refund as long as the request is made within 14 days of purchase, and the game has less than two hours of playtime on it.
"Any game your purchase through the Epic Games Store is eligible for a refund," the updated policy states. "If you receive a refund for a game, you will also receive a refund for all in-app and downloadable content purchases you made through the Epic Games store for that game, so long as that content has not been consumed, modified, or transferred."
Preorders can be cancelled for a full refund at any time prior to release; after release of "any playable version of the game, including beta versions," the 14 days/two hours rule will apply.
You will not be given a refund for any game you've been banned from, however, nor will you get one if it's determined that you're "abusing" the policy, but Epic also clarified that if a recently-purchased game goes on sale, you can refund it and then immediately re-purchase it at the lower price: "We do not consider this to be refund abuse."
The full Epic Game Store refund policy is here.