Super Mario All-Stars (USA) ROM

This is a wonderful game to add to any mario collection since it's 4 games in one! What's included is Super Mario Bros 1-3 and then an addition of the Lost Levels, which pretty much has the same gameplay as the original super mario bros, only a bit more difficult. 
The games are all quite similar, but it's interesting to start with the first one and see how the world of Super Mario progresses. All games start of pretty easy and proceed to more and more difficult levels as you go on. To me, the 3rd one gets hard a little too fast, but the first and second seem pretty average.
All games can have up to two players with an exception of Super Mario Bros 2. You play as either Mario or Luigi, except for in the 2nd one you can choose between Mario, Luigi, Toad or the Princess! A rarity for the older games to have multiple character choices, but a good one at that.
The games are all pretty good, but for me I prefer Super Mario World much more.

The title features complete remakes of all four NES and Famicom Disk System Super Mario titles: Super Mario Bros, Super Mario Bros. 2, Super Mario Bros. 3, and Super Mario Bros The Lost Levels with improved 16-bit graphics and sound. Gameplay, however, is virtually identical, with only the bonus game from Super Mario Bros. slightly different, and some glitches being removed. A few physics properties were changed; for example, jumping and hitting a block in Super Mario Bros. causes Super/Fiery Mario to continue moving upwards after breaking the block, as opposed to the NES version where Mario instantly bounced downwards upon hitting the block. The most notable addition is a save feature: all games now allow the player to save their status at any point in the game. Upon restarting the game, the player will begin at the first level of the world they saved in, with the exception of Super Mario Bros. The Lost Levels, which allows the player to begin from the last level they saved in.