Super Mario Bros. is a 1985 platformer for the NES and now the Virtual Console that was developed by Nintendo. The Wiiviewer did this game as one of his earliest reviews, the 6th one ever.
His assessment of the game was a bit mixed overall, because he viewed it as being guilty of oversimplicity. The gameplay is consistently of the same pattern, and it simply gets harder and harder.
In fact, one of his issues with the game was the challenge factor. It was unfair, in his opinion, to call the game hard, but the few power-ups and lives to start out with make it less preferable for kids to play.
The last major issue was a small one; the spring controls are very finicky in this game, which causes a certain degree of unnecessary difficulty.
Nonetheless, the Wiiviewer says that Super Mario Bros. is a graphically spectacular game for the time, and adults who are up to more of a difficult game will find it to be highly enjoyable, absolutely worth downloading.