According to EA’s FAQ:
”Starting, August 19, 2013 - the Great Game Guarantee (GGG) allows you to return EA digital game downloads (PC/Mac) purchased on Origin for a full refund within 24 hours after you first launch the game, within seven days from your date of purchase or within seven days from the game’s release date if you pre-purchased/pre-ordered, whichever comes first.
“To clarify, we are absolutely honoring the 24 hour and 7 day GGG period starting August 19 - meaning you can refund your un-launched game from August 12; and your already launched game from August 13.”
Exact terms can be read here.
Consider most retail outlets won’t allow you to trade in a used PC game for credit, let alone get a refund if it stinks…