Opinion: The three biggest community Linuxes are Fedora, OpenSUSE and Ubuntu. They're all popular. They're all good. The 'best' depends on what you are going to use it for.
Read it at Eweek
Let's say though that you just want a good, solid Linux that won't give you too much trouble about using proprietary software and codices. Or, you're still getting your feet wet with Linux and you can use all the handholding you can get. Or, better still, you'd really just like to get a brand-name computer with Linux already installed and ready to go. If any of those cases sound like you, then you, my friend, are ready for Ubuntu 7.10.