The original Super Mario Bros. was a classic but both the sequels that were made either didn't advance the gameplay much or drastically altered it creating something entirely different. 3 is the real continuation of the gameplay and mechanics introduced in the first game. The level design, music, graphics, gameplay, power-ups, the introduction of bosses, etc. all make this game a huge improvement over the original. This is still one of the greatest Mario games to this day and is one of the crowning achievements of the NES.