As icarus and others have pointed out..
By definition..
There all simulations..
With that out of the way..
That leads to the next question..
How 'realistic' is the simulation?
Problem with 'realistic' is it means different things to different people.. That is to say ask ten people what it means and you are likely to get ten similar but different answers.
For me the first question about realism has to do with how 'accurate' are the planes performance simulated
One would think that would be an easy question to answer, what with all the WWII performance tests to compare too, but you would be suspired how even that can be debated
If you think that is hard..
Try and debate how realistic the immersion is! Good luck! Because that is a very subjective area that can mean different things to different people. Or better yet, try and debate how realistic the 'handling' of the aircraft is.. Those are the ones that tend to give me the biggest smiles!
In summary.. there is an easy rule of thumb test you can do to tell if it is a simulation or not.. Basically check to see if 'it' is running on a PC.. If it is, you can bet it is a simulation!
From that point on, the only questions left is how 'realistic' is that simulation.
Just my 2 cents on the subject
Dont spend it all in one place