Despite the flickery sprites, I still rate the Amstrad version higher than the other 8bits that I've played.
Spectrum is horribly ported, on top of that, there's a nasty bug that when you play with the Sinclair port, the controls randomly change around. You can still continue using the keyboard, but fuck that! Kempston is fine though.
C64 I'd rate second behind the Amstrad. It's drab palette doesn't do much and makes the Speccy version look more colourful by comparison. It's title tune is pretty awesome though. Always felt the C64 really dropped the ball with all the Dizzies, in retrospect.
Of course, most C64 owners would disagree, but then, most C64 owners thought their shit didn't stink too.