There are no other better engines and what's more, there only two serious competitors out there. CryEngine and Unity. CryEngine has nowhere near the amount of documentation UE has (both official and unofficial) and investing time into learning to work with CryEngine is questionable since the company behind it may go bakrupt at any time and the skills you'll learn are not really usable outside of your project(s) since pretty much no one in the industry (except CIG and Warhorse) uses it. Unity is great for what it is, but it's not exactly the best choice as far as ambitious projects go.