sf in the GE - you can play a center at SF against an actual SF, with roughly comparable total skills, and be very successful. It's unrealistic.
I don't think that there are enough 'pure' SF's made already to see if a C would be successful against one of them.
From what I have seem in games an outside based SF will dominate an inside based SF in the outside game, and vice versa. The only thing I have found is that an inside based SF will dominate the boards, and rightly so.
Unless of course you are talking about a players 'position' as given from their overview page, which I think is very misleading with the player skillset that it gives to SF's