For a limited time (until Friday), you can get Sonic the Hedgehog 2 (the really good port) for free on the Amazon Appstore. Among other free games are Terraria, Worms 3, and FARMING SIMULATOR 14.
Click here to get them. (http://www.amazon.com/b/ref=nav_sap_mas_14_12_24_Dec1_Bundle?ie=UTF8&node=10076151011)