Honestly, you may want to skip NES Metroid and play GBA Metroid: Zero Mission instead. It's a remake of the first game and a fine one at that. It helps link the earlier 2D games to the later Metroid Prime franchise, too.
Don't get me wrong - NES Metroid will always have a place on my game shelf. But it's definitely wanting when compared to Super Metroid, which is still the pinnacle of the series, imo.
Would love to see Nintendo remake Metroid II someday.