I think something that is "complex" and harder to achieve is a far greater "achivement" than something easy to do. I would say it is far "greater" to have pulled together thousands of people and built a totally unique and unmatched technological masterpiece against all the odds with limited technology, rather than one bloke drawing some lines on a piece of paper.
Concorde is exceptionally useful too. I don't know if you've ever heard of Airbus (they turn over about 19.8 billion quid a year, so not a lot) but much of their success can be attributed to Concorde. You see whilst Concorde itself may not have made any money, Airbus (which used much Concorde technology) does. Concorde made many innovations that we see on many aircraft today (fly-by-wire, thrust-by-wire, high pressure hydraulics, full-regime autopilot with autothrottle etc), even in our own lives in fact. ABS... you can thank Concorde for that.
Furthermore Concorde is not inefficient. Inefficient by subsonic standards perhaps but by supersonic standards she is something of a bulimic, even for today. It dosen't pollute either - it actually rebuilds the Ozone layer (although insignificantly
Now in the comparison to the arguably mighty HST, I still think Concorde is the "greater" design. The HST used existing technology and did things that were already been done, albeit not in this country. Concorde was a far greater step in technology and departure from existising designs than the HST ever was - hence a far larger budget requirement.
The HST raised speeds from 100mph to 125mph, Concorde raised speeds from 650mph to 1350mph, quite a contrast. It increased cruise altitudes from 40,000 to 60,000 feet in a stroke as well. Concorde was a step in to the unknown, the HST was simply refining of existing technologies.
The HST used updated carriage design (Mk2 to Mk3) and used two power cars instead of a single locomotive, increasing British speeds to 125mph - something other countries had already achieved. Concorde scrapped conventional aircraft design altogether, with an entirely new wing shape and new engine design, new systems, new technlogies and new ways of solving old problems. It doubled previously accepted limits across the globe in a single stroke.
And what about the icon that is Concorde? As Chaz said, Concorde is recognised globally and is symbol of our nation - can you say that about the HST? Do the majority of British people even know what a HST is or what is special about it? I think not... You ask the same about Concorde and you will get those answers. Perhaps that is what makes a truly great design, one that is iconic and is remembered - the panama canal, the dyson vacuum cleaner, the telephone, the electric light bulb etc, and of course, Concorde.