I'd further that by saying there were many, many ports to ST<>Amiga that were dumbed down for the sake of programming. Yeah, right. Pure and utter laziness to be sure. Competition is one thing, but the mediocre ST did nothing to advance the Amiga. If anything, the ST hurt computing and set it back several years.
Maybe what diskdoctor meant was that Miner's work on the 8-bit Atari's lead to the development of the Amiga. That would be a true statement. ST had nothing to do with Amiga 'cept cripple some of its software at the time.
And yes, lots of cool demo's for the 2600. The homebrews and talent behind them are amazing. Even in 2009, the Atari 2600 is that much more impressive than an ST :-)