I refer you to Nick Bostrom's http://www.simulation-argument.com/simulation.html. The rest of the site is also somewhat interesting.
Anyway, in summary...
So, God could be a teenage AI (which, culturally corrected, could be aeons old and unfathomably wise - or not), running a universe simulation on his gaming rig.
If the rig has enough memory and "CPU", and the simulation allows for it, we may not be alone.
The motivation may be entertainment, or indeed eventual companionship - reproduction.
The prevailing cultural ethos may allow for baby AIs with promising ethical or intellectual makeups to "score" highly enough, possibly through multiple incarnations in different life conditions, to be uplifted to what at least seems to be the Ring-0 "Real" Universe.
The religion you encounter when you get there could be interesting.