Torque 3D MIT is free and give you all the source codes. In other words try to grab a compiler, open up the engine and see how much work ten plus years became
If you like a render engine only under MIT too then Ogre3D is there also with source code access
Have fun and happy coding
"A game that could look almost as beautiful as CryEngine/Unigine capabilities?"
No not really, at least not if you want the engine to be exactly as these two engines as many, many people have worked to get to the point as it is now.
If you only want the graphic then perhaps, but if the physics, sound, AI etc. etc. has to be a part of your engine too then no. The problem is also how much time you wish to spend on it. Grab a MIT engine and make it your own by tweak or just use it for what you like
Edit: thought the above answer needed to be included.