There are three main criteria for this list:
1) size and quality of the library of the system(s) being emulated
2) user-friendliness of the emulator
3) performance/reliability of the emulator
format emulated: Commodore Amiga
This emulator is actually kind of a dick which definitely hurts it. However, the Amiga was a true gaming machine and it actually had a large number of exclusives or games that ran best on it. Actually, a lot of bad Super NES games from European developers were born as good games on the Amiga. Tons of games, great graphics, lots of variety, plus a Euro flair.
format emulated: Apple ][
So far, I haven’t used this emulator extensively but it’s worked quite well to date. The Apple ][ had a large and interesting library specializing in adventures, western RPGs, and other genres not well represented on the dedicated gaming consoles.
formats emulated: MSX, MSX2
Another emulator that I haven’t used a great deal but will in the future, for sure. MSX and this emulator were straightforward and easy to use. The style of the system’s library isn’t that different from a gaming console but it had a lot of exclusives.
#7 Magic Engine
formats emulated: TurboGrafx-16+add-ons, SuperGrafx
note: this Europe-based emulator actually costs money – $20 thanks to exchange rates
A straightforward emulator for a straightforward system that allows you to play the card and CD based games.
formats emulated: NES, Atari 2600, Atari 5200, Atari 7800, Colecovision
MESS is an attempt at a super emulator, able to handle ALL old systems but, for the moment, it falls way short. It is able to do a pretty decent job with the systems I’ve listed but, save for the NES, most of these systems didn’t exactly have awesome libraries. NEStopia is better at emulating the NES but MESS gets the job done and you just can’t argue with this history and importance of the 2600.
#5 DOSBox (with DOSShell frontend)
format emulated: DOS
Current Windows systems are unable to run many of the old PC games from 1995 and before. DOSBox changes all that and opens up a world of THOUSANDS of games, many VERY different from what you’d find on the gaming consoles. DOSBox is complicated, though, so download the DOSShell frontend, which makes the emulator very easy to use.
format emulated: Super NES+add-ons
It emulates the SNES very well and is very easy to use.
#3 Kega Fusion
formats emulated: SG-1000, Master System, Genesis+add-ons, Game Gear
Master System + Genesis alone probably would have earned this spot but add in the gems from the 2nd rate libraries of the SG-1000, Game Gear, SEGA CD and 32X and it’s even more solid.
#2 Visual Boy Advance
formats emulated: Game Boy, Game Boy Color, Game Boy Advance
Thousands of games, many of them GREAT. Now on your computer. Not as comfortable as a real GBA SP in your hand but now you can blow up the screen. And it’s cheaper.
formats emulated: A LOT (most 2D arcade systems)
MAME is a very successful attempt at emulating ALL arcade games. Who knows if it will ever reach that point but as it currently stands it’s able to emulate 90% (my own made up number) of 2D games from the 70s through 90s. It can handle every NeoGeo game, every game from the legendary Capcom CPS1/CPS2 board, and that’s just the start. Most of the 2D arcade legends from Namco, Nintendo, SEGA, Konami, etc. etc run just fine on this system. That’s a whole lot of games and a whole lot of quality. The only drawback is that arcade games aren’t exactly deep and complicated but the combined quantity/quality here earns #1.
WAIT? WHAT ABOUT (insert emulator here)?
Yes, there are a lot of other emulators and systems and I’m not super experienced with some of them. There are also some that just aren’t complete enough to warrant a place on this list but are still worth downloading. For instance, Project64, a Nintendo 64 emulator, runs Super Mario 64 perfectly but has a lot of hiccups on games like Perfect Dark. I don’t especially like the Commodore 64 or Atari 800 computer emulators available and their libraries are also somewhat cancelled out by the inclusion of Apple ][ and DOS on the list. The Sharp X68000 and its emulator are very strong but it’s near-complete reliance on arcade conversions for its library means that MAME effectively cancels it out. Most emulators for 3D, optical-disc based systems are still pretty unreliable unless you love changing plug-ins and settings for every game, so no PlayStation or Saturn on this list. And systems like PS2, DS, Xbox, etc.? Go BUY THEM AT THE STORE.