There are many science fiction stories about real people entering a computer game. Tron, Only You Can Save Mankind, The Amazing Digital Circus etc. etc. So that part isn't distinctive. Giving the game the same game mechanics and / or goal as Sburb would be more of a problem. Interacting with aliens from other worlds / universes via the game? I think you'd have to come up with some very different reasons as to why and how that happens.

I wonder if Andrew Hussie has ever given their views on this? Also, a number of MSPFA artists over the years have re-written their HS fan comics to be original works. I'm not sure how many of those have kept the Sburblike elements.