The NES Classic Edition system is a miniaturized version of the groundbreaking NES, originally released in 1985.
Just plug the NES Classic Edition into your TV, pick up that gray controller, and rediscover the joy of NES games.
Castlevania II: Simon’s Quest™
Donkey Kong Jr. ™
DOUBLE DRAGON II: THE REVENGE
Mario Bros. ™
MEGA MAN® 2
Punch-Out!! ™ Featuring Mr. Dream
Super Mario Bros.™
Super Mario Bros. ™ 2
Super Mario Bros. ™ 3
The Legend of Zelda™
Zelda II: The Adventure of Link™
That's a pretty good selection, though it's a shame Castlevania III isn't included, as I feel that's the best of the NES trilogy. Tempted to pick it up at some point; it'd be easier than pulling out my NES and setting it up again when I'm in the mood for some really retro gaming, and far more portable besides.