I guess it would be fair to say that some of the major players are debian (or ubuntu), fedora core, and suse.

I haven't had any personal experience with suse, so I can't comment on that.
I've always felt it was a bit over-bloated for a linux distro, though.

debian/ubuntu have the advantage that they probably sport the easiest package update/install/uninstall system (apt). apt seems (to me) the highlight of these distros.

fedora core has yum (the equivalent of apt), but I personally have had a few stability issues with it. Maybe it matured more lately, last significant experience I had with it was in FC3.
Another problem that FC used to have (don't know if it still does) is upgrading from FCx to FCy (y > x). That was absolutely impossible to do up until FC4 or such. Don't know if it's better now.

One of the downsides of debian/ubuntu is that it's a bit of a pain to install it - awfully unfriendly, and it might make you feel a bit lost during the process.

Anyway, you should give a bit of thought to what exactly are you gonna use your linux box for ? Will you care about upgrading packages very often ? Will you care about migrating to a new distro (e.g., FCx to FCx+1), or will you rather just install the new one from scratch ?
Are you only concerned with a friendly installation process ?
Depending on how you feel about these, some of the points I made above may have more or less importance to you.

hope this helps.