I'm not sure they count as they might not be exclsuvly Amiga but mine were Peter Molyneux, Ian Bell (for Elite but I don't know if he actually did anything for the Amiga version) and of course who could forget David Braben - just reading his interviews with his really epic ideas for space games was facsinating to me.
Sid Meire too must be mentinioned again (I see he has already) for what he's done for gaming right through to this day, just looked at his list of games he's worked on - amazing!
http://en.wikipedia.org/wiki/Sid_Meier
