From the top to the bottom, in order are the best to least best but still good Linux distributions as there will never be one version of Linux, as there is only one distribution for Windows or Mac OS X.
Pear Linux 5 to me is probably the closest looking Linux distribution that looks anywhere close to every aspect and feel of Mac OS X. As it was released in July of 2012, it is the fifth iteration of the Pear Linux OS that is now available for download. This OS was previously known as Pear OS and also Comice OS, and always has been included with thousands of different free applications and is designed to do everything you want it to do. I have not run in on my machine before, but I think that it’s typical for most linux distros to work on almost any desktop PC. Also, this OS is built upon the GNOME 3 interface, and is powered by Pear Linux Shell which is a mod of GNOME Shell and is set up to look like the Mac OS desktop. Last but not least, I’ll mention that it has it’s own App Store.
2. Ubuntu with Macbuntu theme
Apparently this is a Mac OS X Transformation Pack called Macbuntu. Obviously open source, it is designed to transform the appearance of Linux (or I should say Ubuntu) to look like the layout of the Mac OS X environment. Macbuntu’s team has dedicated their work to an Ubuntu Linux OS, which can be used in other OS’s based on Debian/GTK. The project began in August 14th, 2010. You can find the project download here.
3. Dream Linux
Full of multimedia tools and being a distribution of Linux made in Brazil, this is made for people who like to create. The Rocket Dock allows it to be a very nice looking desktop environment and also last but not lest the XFCE Desktop, with both it makes a nice Mac-like environment. Installing this distro is very easy and you only need to use one wizard. Another upside to Dream Linux is that it’s Debian based, which is more lightweight than Ubuntu.
The users of this OS was boosted when it was installed on linux PC’s sold at Walmart in the U.S. (maybe other countries additionally), being named the “gPC”. Though it didn’t come with a “smart blue” look the developers felt it needed a greenish look in it. gOS is a pretty slick feeling distro (aswell as the boot time). It’s not known if they use Rocket Dock or AWN, but with the LXDE installed, gOS feels like a good option for netbooks. Google Apps is what this distro heavily relies on apparently.
This debian-linux based distro is what’s made by Enlightenment. Despite it being an OS to show off the latest and greatest of the E17 Desktop Environmental modes, this Mac-like distro has many routine users (as said by Distrowatch). You can check out more Enlightenment DR17 screens and features here, which includes the iBar Dock.
As most distro’s have weird names, sometimes named after food or aliens, Puppy Linux is a very good distribution of Linux that is good for older computers. An individual from the community thought the regular desktop was not click enough so he created this OS X modification for it. This modified version of Puppy provides speed, a simple user interface, a taste of Apple, and some very cool Puppy applications.
If you wish to change a more popular distro like Ubuntu or Fedora to a Mac OS X-like look, you can check out some of these Linux docks.