I'm gonna go ahead and say the Amiga, where it was originally released in 1993. Shame that the site doesn't even mention the Amiga version at all :/ Edit: Well, I have to correct myself - Qwak actually first came out on the BBC Micro, a lot earlier than I thought. Still, the Amiga version is the "closest" graphically (and probably gameplay-wise) to the modern versions.
Just noticed that the original post is old AND by the original author. Fun little game. I had the Amiga version years ago and bought the GBA version a couple years back. I haven't tried it on the iPhone yet but the screens look good.
