Open world games could be alot bigger.
Anyway, you may want to keep an eye out for Star Citizen on PC. It will have an epic space world to explore and do things in. It features a lot of hand crafted content with some procedural generation as well.
ARMA III on PC also has some very large environments worth checking out if you just want to explore and conduct various army operations.
The Crew has the entire USA in condensed form to drive around in. It is a decent game too now that it has received some big updates.