Tip: Remaking levels from other Mario games is strongly discouraged, especially popular ones (World 1-1 from SMB or SMB3, for example), as their over-presence in Mario games, official or not, often makes them uninteresting to play.
bsnes is a Super Nintendo / Super Famicom emulator that began development on October 14th, 2004. It focuses on performance, features, and ease of use.
bsnes currently enjoys 100% known, bug-free compatibility with the entire SNES library when configured to its most accurate settings, giving it the same accuracy level as higan. Accuracy can also optionally be traded for performance, allowing bsnes to operate more than 300% faster than higan while still remaining almost as accurate.
bsnes is fully open-source (GPLv3) with public development occurring on GitHub.