Given I'd probably only know as much as I saw on the back of the boxes, or maybe an in-store display.....Maybe Sega Master System. It had the 3D and arcade games I liked at the time like Outrun. However, by 1986 Metroid and Zelda were out on the NES. It would be a toss-up, without significant knowledge.
One thing's for sure, no chance I'd pick the 7800, the graphics alone being an easy reason.