It's been a long time, but I remember us having this discussion in the very beginning. It was decided to list the categories by the name they were marketed under. You never saw anything that said "Nintendo Super Nintendo", just "Super Nintendo". Also, I don't seem to remember anyone saying "NEC Turbografx 16". I think it makes sense for the Sega consoles to have "Sega" in front because that is always how I heard them marketed back in the day. It was always "Sega Master System" or "Sega Genesis" etc.