In the following tables, the most important Genesis-emulators for DOS and Windows are listed. The speed rating refers to the emulator running on my own systems (an AMD K6-2 400 under WinXP and an IBM Thinkpad 600 under WinXP). The compatibility rating is based either on Sam Pettus' MegaChart or on some bench testing done by myself.

There are two other emulators for the Genesis (WinAGES and retroDrive) - but their primary purpose is to emulate the Genesis AND the 32X (plus, in the case of WinAGES, the Sega CD), hence they are discussed on the 32X and Sega CD pages of this site.

Beginners should eventually start with Genecyst, because it is the emulator easiest to use with its nice mouse-driven GUI. It also offers the best sound emulation, almost as good as the real system.

KGen98 has the edge over Genecyst in all categories except sound, but only has a keyboard-driven user interface (which, of course, is no drawback at all if you know how to use a keyboard ;-).

If you prefer Windows-based emulators, GENS is the best choice you can make. It is very fast, offers a very high compatibility rate and some nice video features such a 2xSAI engine and neat scanline modes; moreover, it also emulates the Sega CD! DGen comes very close to GENS' excellence, but is a lot slower. If you want to hear almost perfect reproduction of Genesis sound, this is the emulator you need to try. Megasis is also a good choice, but it is even slower than DGen and (at least for me) crashes rather often due to some unimplemented CPU features. Just recently, Atani has released the first version of his emulation project SegaEMU. Currently it is rather slow compared to other Windows-based emulators, but that will hopefully change in the future. It is definitely an emulator one should keep an eye on. Xega is newest emulator in the bunch, and it also emulates the Sega CD. However, it is still in rather early development stages, though it already offers some nice features.

Since the recent version, the quality of VGen has improved significantly, so you should give it a try, too. Jason constantly improves his emulator (as I can see from the private betas :-), so everyone should keep an eye on this emulator.

If you are a Genesis programmer, you will find either GENS or VGen very useful because those two emulators have debugging features. GENS leads the way here.

The emulator St0rm, was started by a Spanish programmer and is now continued by Kaneda. He's making nice progress. The other "new" emulator, Genital (written by Bart Trzynadlowski is also making good progress, and it is the only emulator which can handle the few Menacer games (sort of).
 
The other emulators, MESS, Generator and the oldie GenEm, are not worth getting. They are in very early beta/alpha stages, so don´t expect very much games to run on them. However, if you want to emulate the Genesis under Linux, you have no other choice than to use Generator or GenEm.