Well I had C128, and Amiga 500 & 1200... As a coder and composer, I can guarantee, I'm much more creative with hardware limitations.
And if I look at the platforms: C64 was a bit to restricted, and A500 had far to much to offer. I enjoyed using exploits on C64 to achieve the unimaginable (here are a few tricks I'm talking about: http://en.wikipedia.org/wiki/Commodore_64_demos). But Amiga had much more processing power, everything could be done with planar graphics - where's the fun in that?
Not to mention the SID, love the sound of it - and sampled music just can't replace the analogue synths.
You've mentioned C128
But you're right, C65 was discontinued because of the Amiga - it was cheaper and faster...
Ps: I mentioned the C65 because, if Commodore is really making the C64 (x86) PC, they should rather finish the C65 project.
FORTRAN is for pipe stress freaks and crystallography weenies.