NonMAME is the definitive source for all known arcade emulators that either support games that are not in MAME, or provide better emulation of games that are in MAME.
NonMAME only documents games that were featured in actual arcades; this obviously excludes homebrew "hacks" and other such nonsense.
NonMAME only documents emulators that run games faster than MAME if they are unplayably slow on MAME using the baseline reference system noted below. This is due to the site's focus on accuracy above playability. From a preservation standpoint, it is more important to emphasize documentation of the target hardware than the host platform, which will in theory reach speeds fast enough to run any emulated system given enough time.
Evaulation criteria for the best emulator of a given system is as follows (in order of importance):
2. Open-source status and cross-platform availability
4. Features (joystick, network play, etc.)
6. Future release potential