The NES Control Deck needs 9 to 10 V, at least 850 mA. Polarity is not important because it uses a diode bridge rectifier. Center negative, center positive, and 9 V AC will all work. Thus the AC adapter for Famicom, Master System, Mega Drive/Genesis model 1, or Sega CD (all 9-10 V DC center negative) will safely power an NES. For example, a Sega MK-1602 (for Genesis) will provide 9 or 10 V DC depending on revision, center negative, at up to 1200 mA. A Sega 3025 (for Master System) provides 9 V DC, center negative, at up to 1000 mA. (See
specs and photos at Sega Retro.) It's OK to use an adapter that provides more current (mA) than you need; that's called "headroom".
But don't try using the official NES-002 adapter on a Famicom or Sega system. It'll fry it because these systems can handle only center negative, not the AC that the NES-002 produces.