Yep. I just checked my emulator archive. The first version of Genecyst was released on 30th June 1997. However, GenEm was released already in 1996.
Still, you can call Genecyst the first decent Genesis emulator.
What counts though as well is the usability of the emulator. GenEm had very little compatibility, only very few games worked. Furthermore, development was
Genecyst definitely was the first usable Genesis emulator, and for a bit the best one – until KGen came by on 18th August 1997. The last KGen version 0.34b was for a long time the best Genesis emulator – until Kega Fusion came by. 🙂
