Clearly a biased opinion...
Did you know that there're many exclusive Atari ST games (and numerous great demos too)?
http://forum.classicamiga.com/forum/showthread.php/2322-Exclusive-Atari-ST-games-that-were-never-ported-to-the-Amiga?p=25974#post25974
I had a great time with my Atari STe, but also enjoyed the Amiga 600 / 1200 later on, but never gave me the good feeling I had with my ST for some reason, even if these machines were superior.
Especially the Atari ST demo-scene was very active back in 87 - 90.
But the Atari ST was only popular in some countries like France, Spain... When I moved from France to the Netherlands, my ST became obsolete very fast because the Dutch people are very Commodore-minded.