Then I have to say Sid Meier (I say Sid Meier, because it's mostly his games I found interesting, most of the other games from Microprose didn't interest me much).
Team 17, simply because they were THE trademark of the amiga.
Sensible Software, don't need to say much about that one, do I?
LucasArts was one of my favourites back in the days, but now they're just an empty box in a corner to me.
Sierra were also on the top on the Amiga, and everything went downwards from then. And how could they actually fire Al Lowe? Roberta Williams? Talkabout suicidal tendencies.
Squaresoft made one of the greatest games ever for me, Final Fantasy VII
Oh, and Konami makes Metal Gear Solid, another favourite of mine.
Too many greats...