The logic that people are too young to remember when the brand was good could extend to virtually every 'retro' marque still in production (certainly by this communities definition of a desirable bike).
I love GT's, but they are boring and never really achieved cult status here BITD. Some big races were won on them, and Hans Rey did make them look cool, but i think they were always overshadowed in the UK. Maybe if this poll was on a German based forum, everyone would be going nuts
As a footnote, i also wonder if price was a factor? Kona made desirable bikes right from the bottom of the range, perhaps it was the case low-end GT's were rubbish and the top-spec ones weren't exotic enough to be desirable (compared with Kleins etc)?
I lusted after an RTS as teenager, but nobody i knew rode any sort of GT. Plenty of Muddy Foxes, Konas, Specializeds, Oranges etc though.
Just some more ideas to kick around...