Depends. The fact that there was never any fluids in it means that you won't have varnish (from the gas) or acids (in the oil) to deal with. You might have some corrosion for all this time, but chances are the thing was packaged up well enough at the factory to have a pretty long "shelf life".

If they fire it up and it runs for a few minutes without excessive smoke, it's probably fine.

Don't forget to put oil in it first.

The best thing to do might be to remove the spark plug and put a little bit of motor oil into the cylinder. Fill the motor with oil as directed by the maintenance instructions. Then turn the motor over slowly and let is sit for a day or more. Turn it over a few more times and then replace the spark plug. Fill it with fuel and try to start it up. You may have to remove the plug and clean it once.

I think the engine/generator will probably be fine. If, however, after starting it you do not get any AC voltage out of it, don't worry. Sometimes from sitting for so long the field coil has lost it's magnetism and needs to be "flashed."

A simple procedure sometimes outlined in the owners manual or easily done by a small engine/power equipment repair shop.