Sad to see Silicon Graphics so far down this list.
IRIX Indigo Magic Desktop was the Rolls Royce of user interfaces in an era when Apple computers couldn't even do multi-tasking and PC's still had an interface (Windows) that sat on MS-DOS. Linux was a 'toy' with a GUI that was positively 'off-brand' and the Sun version of X-Window was just plain awkward, clunky and slow. Meanwhile, on SGI computers, you could have a 'CPU eater' 3D rendered desktop background with real-time video compositing in 3D scenes going on in your programs.
SGI computers were also 'useless' at things normal people used PCs for. So no spreadsheets and certainly no word-processors. Games were also lacking, yet so many games were built with SGI machines.
Regarding the design of the boxes, nothing exuded power and awe in quite the same way. Racks of SGI hardware made a place 'mission control', other stuff is just data centre plumbing that just does not project a futuristic vision of cool. To take an automotive analogy a gaggle of SGI machines was more like a Formula 1 grid of cars whereas any other computers en-masse just looked like a supermarket car park.
There was something accessible about video and 3D on the SGI machines that has not been seen since. Hardware may be better today but it does not compel you to want to play with it.
I blame Microsoft for destroying SGI even though there were problems with the wider SGI management and business model. We ended up with a 2D flat web whereas had SGI been around then I am sure that things would have been 3D, in the browser, as per the awesome demos that came with the machines back then.
I wish more tech businesses were about the greatest common factor, and not the least common denominator. If I could find a place like SGI to work, I would camp on their doorstep until they let me in.
The thing about SGI back in the day was that it was more fun to work in TV, movies, geology, weather forecasting, serious computing at a respectable university and so on. I never aspired to work for SGI but knowing how to turn the behemoths on and type a few commands kind of got me working in disciplines that normally required extraordinary levels of study and professional dedication, e.g. meteorology.
I am glad that Open Inventor lives on!
However, IRIS Explorer, remember that one? That was awesome and I wish it existed today. My peak time for playing with IRIS Explorer was when I had my first SGI box, an early purple box Indigo. I think I had the super-deluxe 'Elan' model, but that was still under-powered for Iris Explorer. In latter times when I had a small fleet of Onyxii and O2s at my disposal I didn't have access to IRIS Explorer.
NAG in the UK bought IRIS Explorer and didn't port it to more modern computers. At least this was a better fate than what happened to CosmoWorlds, this was sold to Computer Associates who killed it.
In an odd way I think that the world was better when it cost $100000 to have a decent computer on your desk. You valued your time more.