I have to say about 1996, When their CPU/GPU combo of brute force could finally run the games that the elegant hardware design of the Amiga made possible in 1985.
Of course for me the way that AmigaOS feels has never been duplicated for me. I'm not just talking about warm sentimental feelings but something about the way that it responds to the user vs. other OSs be it Windows, Linux or BSD-Mac.
for one wish so BADLY that the OS will be Open Sourced. I wish some rich old Amiga user would buy the rights to the classic OS and Open Source it. I'd love to see what we could do if we had the source code and could do it as a Open Source project.