Amiga is what Amigans think it is (take a look on Macintosh)
Is it a Mac an MacOS 9 powerMac? (different CPU 68k->PPC)
Is it a Mac a macG5 with MacOSX? (different OS)
Is it a Mac a computer with an Intel cpu? (next generation macs)
Same thing for Amiga.
For me an Amiga can be classic, AmigaOne with AmigaOS 4.0, Pegasos with MorphOS, Aros in an x86/PPC/68k box. (we are like the BSDs right now

we got 3 choices ;-))
PS: well thats 4 but classic 3.x doesnt really count anymore

, the classic hardware on the other hand can use the other three OS options I mentioned.