It depends, if you want an engine that you can use to do 2d with/without parallax effect, 3d with a lot of community behind then Unity would be a great idea 'cause you can export your game for Android, iOS, MacOS, Windows, Playstation and Xbox. The bad thing about it is that for publishing (just publishing) you need to pay for a license. Otherwise Unreal is a great tool too, as I understand how they charge now is that when you start selling more than a specific number of copies they start charging you with a % of every copy you sell