Fifteen years ago, there was something of a competition between two SNES emulators: ZSNES and SNES9x. ZSNES was a bit faster, and SNES9x a bit more compatible, but both of them ran relatively happily on a 100MHz 486, and that was that.
Not much has changed since then. The latter remains a bit more compatible (now notable for being the easiest way to run the recently translated original Super Famicom release of Tactics Ogre, as well as Nintendo's inventive, never-released Star Fox sequel). Getting SNES9x going is pretty simple: Just download the emulator, unzip the archive, run it, and select File -
> Load Game.
Both apps support Internet multiplayer, cheats, and a number of image upscaling techniques. For image upscaling in SNES9x, you'll want to use the Display Configuration menu, under Options. Chunky-pixel diehards should uncheck bilinear filtering and ensure that the Output Image Processing drop-down list is set to none. Futurists will want instead to start with an output processing setting like hq3x--which effectively triples the SNES's resolution output from a native 256 by 224 to a still-reasonable 768 by 672--and experiment from there.
Perhaps the most important SNES emulator feature is a fast-forward button. After all, many SNES classics (Final Fantasy VI, Chrono Trigger, Earthbound, and the like) are role-playing games that move along at a glacial pace by today's standards. Pop the fast-forward button, and your SNES emulator will hum the game along at double or triple speed on any vaguely modern computer--great for power-leveling.
For users who want superfaithful emulation, a third option is the somewhat infamous bsnes. While not for the faint of heart--it requires between ten to twenty times the CPU power that other SNES emulators do, and its somewhat stubborn creator has a tendency to revamp the entire GUI in each new release--it promises to deliver an SNES experience with uncannily bleepy and bloopy authenticity.