Super Mario Bros. Deluxe (USA, Europe) ROM

This is a remake of Super Mario Bros. (which was an NES game) on the Game Boy Color. There are a few extra bits added, though, including a 'challenge' mode where you pick any level you've already beaten in the normal game and play it with no checkpoints and five red coins hidden somewhere. You get medals for finding all the red coins or getting higher than a certain point total.

If you get 100 000 points Boo will appear on the menu to challenge you to a race. If you select him you will enter 'You vs. Boo' mode where you race Boo to the goal flag on eight special courses.

You can also unlock special pictures by various means and print them out with a Game Boy Printer (I don't know if you can do this on an emulator though).

This game is basically a remake of the original Super Mario Bros game.
For some reason, it was more impressive on the Gameboy Color than it was on the SNES. Perhaps because the gameboy didn't have as many good games (particularly Mario ones) on it, but I really enjoyed it on here.
You play as Mario, and your object is to get through each course in several different worlds. At the end of each world there is a castle in which you must complete and a boss at the end, although these bosses are never too complicated to beat.
To me, it seemed as though it got very hard very quickly. It was a little frustrating, but it didn't keep me from playing it.
Definitely a good game, and it's Mario - so how can you not like it?