1) SuSE
2) Knoppix
3) Red Hat
4) Ubuntu
5) Slackware

Knoppix was the first famous Live-CD (and non-commercial!!) and for me and I really think not only for me it was the first Distro on a PC I bought without any OS and I -as a absolutely non-tech managed to install it (due to a outstanding tutorial in German written by Fabian Franz) and get productive with Linux.
Even though I see myself still as a non-techie, I am a GNU/Linux-only user at home.

Mandriva (originally Mandrake) makes my personal top 5 list, as it was Ubuntu before Ubuntu was cool – a remix of (in their case) Red Hat intended for the desktop newbie.

I had tried Red Hat first and given up, because I couldn\’t get it to do anything. A friend recommended Mandrake, and suddenly the advantages of Linux were obvious to me. I\’ve never gone back, though I did eventually migrate to Ubuntu.

(Mandrake lost a trademark lawsuit from a magician-centered comic strip of the same name – their prominent use of a magical top hat and shooting star probably didn\’t help – leading to the name change to Mandriva a few years back.)

I recently tried Kubuntu, and was very disappointed with KDE 4. A friend recommended Mandriva (deja vu!), and sure enough, it\’s an excellent and quite polished KDE 4 distro. Should I decide to switch to KDE 4, life with Linux will have come full circle.

Currently, Mepis is my favorite Debian derivative.

I also think the Knoppix should get a mention… I think it is mostly because of Knoppix that most Desktop Linux distros have a live CD/DVD today.

The distros that developed the common package managers have really allowed GNU/Linux to thrive, particularly Debian and RedHat. These packaging systems made GNU/Linux much easier to deploy by amateurs and professionals alike, a very broad spectrum of computer users. They also made it much easier for new distros to develop and to fill every possible niche.

I believe 2009 was the Year of GNU/Linux on the Desktop as most OEMs shipped it and the number of people in the world who have not heard/seen/used GNU/Linux dropped quickly with the netbook. 2009 was the year that GNU/Linux became mainstream on the desktop as it has been for years on the server. M$ took a hit to the bottom line over GNU/Linux in 2009. About half the people I offer to install GNU/Linux accept these days. People see it and want it.

@mercibe: What about Moblin or ChromeOS? I think the next major (as in historically significant) distro won\’t be a desktop distro but a Netbook/Cloud distro.

If we can\’t win in the Netbook market with Moblin, which is clearly superior to Windows for that hardware, then we\’ll never win. If Moblin fails to displace Windows in Netbooks this year I will really feel that the distro community has dropped the ball.

And to be clear, I want it to be installed at the factory. I don\’t care how easy to install it is, if the user has to do it that\’s an extra step that won\’t get done.

Slackware – duh!

Red Hat Linux – First commercially viable distro and first to capture public\’s attention in any large numbers. You can practically attribute the widespread use of Linux to Red Hat.

Debian – duh!

Mandrake – First truly desktop oriented distro for the masses complete with easy installer and GUI tools.

Knoppix – First? LiveCD and definitely the first widely distributed LiveCD, if not. It opened the doors foor all the Debian spinoff distros like Ubuntu.

Caldera was mediocre at best. Their only claim to fame being the first real Linux to try to get on commercial desktops. Unfortunately they probably turned more people away from Linux than to it.

That being said….
1. Slackware
2. Redhat
3. Debian
4. Knoppix
5. Ubuntu

regards

from http://www.gentoo.org/doc/en/articles/making-the-distro-p2.xml
—–
When you put together a Linux distribution it\’s really important that any bug fixes you create are sent upstream to the original developers. As I see it, this is one of the many ways that distribution creators contribute to Linux. We\’re the guys who actually get all these different programs working as a unified whole. We should send our fixes upstream as we unify so that other users and distributions can benefit from our discoveries. If you decide to keep bug fixes to yourself, you\’re not helping anyone; you\’re just ensuring that a lot of people will waste time fixing the same problem over and over again. This kind of policy goes against the whole open source ethic and stunts the growth of Linux development. Maybe I should say that it \”bugs\” us all.
—-

Mandrake 7.0 changed desktop Linux for good. It had long left its position of Red Hat + KDE and became a seasoned product with it\’s own solutions like the control center/drake tools and URPMI. It was a game changer, and many older Linux users point to Mandrake 7.0 being the first distro they could actually use and understand.

Ubuntu, IMO, is still little more than warmed over Debian. It doesn\’t even stand on it\’s own two feet, like Mandriva does. It has to rely on Debian to do the heavy lifting. That, in my mind, doesn\’t put it in the same league as the other distros given, except Knoppix. Knoppix gets cred for being the first, though, and changing the game.

Caldera gave us the per-seat license, the buying of dead item like DR-DOS and aggressive litigation, the buying of licenses from unpopular failed distros and the adoption of different names for more and more litigations. Caldera showed us that you don\’t have to be Microsoft to be predatory. Remember that Caldera became the tail wagging the dog behind SCO and its infamous lawsuit.

And on top of that, Caldera was the first to outsource lousy support for its \”product\”. Believe me,I ran an office system on linux in 1997-2000 from router to servers to desktops, and I bought Caldera and shortly abandoned it after experience with their \”support\” which dismally failed to return three phone messages and sent an apology only after I sent in an email complaining.

Of course, WordPerfect was sold many times, but one company that had it actually issued it for linux. There was another face-changer. THat outfit proved that you could develop dynamite extensions for a desktop and then paint yourself into a corner by refusing to share tham back into the community. Any other readers remember the company? I still have one of their disks. Corel, the mental midgets of the trade, did a beautiful extension of KDE 1.4 and then would not share.

Actually, there was a time when it appeared Linux was forever destined for servers only. Then a distro took the public portion of RedHat and combined it with KDE version 1. It is not to be measured in terms of its own very modest success but in terms of its support for open-source and forever changing the fate of desktop linux. No one would have done much with the desktop had it not been for the very outstanding initial success of Mandrake Linux in 1998-99. Moreover, the email help lists it initiated were the most friendly around. Red Hat help lists required flame-retardant underwear at the time.