I read somewhere, that there was a MorphOS developer using QEMU at some point.
I enjoy all variants of AmigaOS. However i believe as mentioned before, only original Classics 68k are Amigas, the rest are Amiga-like.
Speaking about Amiga-like OSes, my personal recomendation for a choice is like this:
1- AROS - Works in Inexpensive x86 hardware, and has progressed a lot in the last 2 years. It certainly has a future and it is free.
2 - MorphOS - The most mature AmigaOS-like, but still with issues (slow network speed). It is really cool. The downside is that it has no realistic hardware future (PPC Macs will eventually become slow in the future, as software evolves continuously with more resource hungry applications) and, PPC has long left the massive user market it once had.
3 - AmigaOS 4.x - It is a really one hell of a buggy OS, it seems like it was a rushed job, and that the devs are still fixing major bugs. Its hardware is overpriced and underpowered. The good aspects of it, is that it feels like an easy transition from AmigaOS 3.9, and that it has the official "Amiga" name on it.
If you want a system with a perspective of future go the AROS way
If you want something cheap go for AROS
If you want a polished system with the best performance per mhz go MorphOS
If you want something with the official "Amiga" name, go AmigaOS 4.x