What its the best game-engine 3D to Python 3.x and easy to install on Linux (Debian 7 "wheezy")?
Not sure if it is the "best" - but not working on the field I am aware of few others than Blender 3D 's  game engine. Blender moved to Python 3 scripting at version 2.5, so any newer version than that will use Python 3 for BGE (Blender Game Engine) scripts.
Pygame is also available for Python 3.x, and it does feature a somewhat low-level interface to OpenGL - -sou you could do 3d with it.
Both should not have any major problems running in Debian, but maybe you will have to configure some sort of PPA to get packages being installed for Python 3.
Also, be sure that your Debian's python3 is 3.2 - this distribution is known to have surprisingly obsolete packages even when one is running the most recent one.
Game Engine 3D to Python3.x?