And a big part of the difference is the environment:
On the server you have a relatively homogeneous hardware platform, many deeply technical users who can and will fix things that are broken, and good connectivity of related environments so that useful innovations spread quickly and the people who made those innovations possible benefit from their spread.
On the desktop you have a much less uniform hardware environment, relatively sparse numbers of technically able users, multiple obstacles to connectivity, and almost no individual recognition for people who make important improvements.
And the problems that are being solved are different, desktop software usually has to put up with a lot of bureaucracy and rules; writing desktop applications requires that developers be aware of the conventions of the system they are operating in and play well with a host of other software for something as simple as drawing a dialog box for the user and capturing input from it. On the server it's relatively easy to partition processes from each other so that they don't interfere with each other; whereas on the desktop you have to support every conceivable action that someone could possibly take.
That said, Linux "winning the desktop" isn't necessarily a worthwhile goal. Don't get me wrong; having Linux desktops available is a good thing all around, it keeps Apple and Microsoft honest. And it's unfortunate that intellectual property concerns have hobbled the development of multimedia in open source to the extent that they have.
Do we really need more WIMP style desktop operating systems that are attempting to be familiar to both Mac and Windows users?
Shouldn't Open Source Desktops be a hotbed of innovation? A carnival of new ideas, metaphors, experimental interaction designs?
But if you look historically at most major open source projects, they aren't innovative. IMHO, most open source projects seem to stem from a desire to have a free (in both senses of the word) version of xyz proprietary/closed source software.
So we end up with lots and lots and lots of copies/equivalents to closed source software, only with a few esoteric additions for whatever itch the author needed to scratch and half the feature set gone.
Sometimes, the OSS version gets better over time, and even supplants the closed source version. But just as often, once the author scratched that itch, development stalls and very little innovation happens. Or alternately, we'll see dozens of entirely different reinventions of the wheel, where somebody didn't like the particular way the OSS version worked, and then just rewrote the whole thing again. I mean really, how many half baked personal finance software tools do we need?
In all of this, what doesn't tend to happen is novel innovation in desktop software. Open source games are rehashes of closed source favorites (I mean really, can anybody point me to a completely novel OSS game)? Desktop software tends to be free (as in beer) copies of expensive proprietary software (GIS tools, image editors, 3d modelers, laboratory tools) or non-user friendly academic research projects released into the wild. Taking gaming as an example, almost all of the innovation is happening in the closed source, indie gaming scene.
Basically, you can kit yourself out with less polished version of hundreds of thousands of dollars of proprietary software for free (that you can play with the code a bit), but that's about it.
OSS is sadly trapped in a cycle of non-innovation and has been for years.
iTunes and WMP are bloated crap that force you to sit through DVD warnings. WMP has gotten a lot more stable since Windows 7, but that's actually a case where it has taken Microsoft years to come up with anything approaching the usability of VLC. (And their fealty to the MPAA prevents them from taking the final user-friendly step and allowing us to watch what we want to watch on the DVDs we've purchased.)
Chrome is widely regarded as the front-runner among browsers. And to be clear, Google didn't make Chrome because they wanted a free (in both senses of the word) browser. They built it because they wanted a browser that doesn't suck. (Though I guess you could make the argument that KHTML was just a me-too product.)
I don't think Inkscape has any competitors, open or closed. It's an intuitive, full-featured vector graphics editor. Adobe Illustrator by contrast is certainly superior, but it has a learning curve that makes it unusable for people who aren't graphics designers. Inkscape is extremely innovative.
Other open source products I can think of with fantastic UX are Transmission (the BitTorrent client) and Colloquy.
I'm not sure that is a victory of OSS as much as it is that they have more freedom to play fast and loose with patents than a commercial/closed source developer would have if directly selling their software (particularly in the US market).
Most software isn't innovative, and open source samples from the same intellectual gene pool.
EDIT: This is more like what I used to look for back in the day: http://www.osnews.com/topics/1 There's a list of available topics at http://www.osnews.com/topics/
Only if you don't want them to be used. Which is totally okay, but it'll keep most people (myself included) far, far away.
Last time the Linux desktop felt innovative was the release of enlightenment 0.16. I had 9x virtual desktops and a completely skinnable UI with a reasonably robust scripting language running on some POS Dell laptop, and it was speedy.
You are right, and my comment wasn't very clear on this part.
It was just to avoid the comments saying that I am an open-source hater.
Having an opinion about the miserable state of the Linux desktop has nothing to do with open-source advocacy. The success of many open-source projects including Linux itself (on everything but the desktop) is proof that the model works, and can produce quality software, often better than the proprietary alternatives.
I too am an open-source advocate, and I've met insult and disdain when I rant about the desktop "holy cow". There's just something there that makes people blind to the issues, and it's the same thing that makes the issues pile up and not get fixed. It just doesn't happen very often now because I seldom give enough of a crap about this long-lost battle to even enter the discussion.