When I imported G3.5 planes into G4 they seemed to have a little less detail. Of course the graphics will be limited by the graphics card. I had a fairly good graphics card (GeForce 9400 GT) and couldn't get the detail shown in the "screenshots" of G4 let alone G4.5.
Like I said, I sold G4 and use FMS now. I really don't miss the details, once you fly a few feet away it looks to me as good (or bad) as FMS.