Mega Mario is intended to be a remake of the original Super Mario Bros game, featuring improved graphics and smoother movements, but I must say it falls quote short of the expectations.
The game does actually recreate the original adventures of good ol' Mario, including the original scenarios, enemies, bonuses and even background music and sound effects.
However, graphics are far from having been improved at all. Also, movement feels awkward, in the sense that when you press the spacebar to jump, Mario takes a while to react and moves like being recorded in slow motion.
That said, you can still have fun with this clone, especially by creating your own levels with the built-in editor.
A basic Super Mario Bros clone with all the original game's elements, plus a level editor.