The best OS for newbies really depends on the UI. Windows would be the worst as it has things that are laid out so poorly that even I get confused trying to find basic controls. OS X is actually a close second as many of the things that I often get “under the hood” for are just plain locked out.
That leaves Linux, which covers a wide range.
You have the Linux that everybody thinks of; the old Bash shell CLI. You have embedded systems like the Siemens controls on the Handtmann SC 5-axis mill I use at work. You have Android and it’s derivatives (like the Nook and Kindle use). then tehre are the desktop shells; KDE, GNOME, XFCE, MATE, Cinnamon, Unity, Pantheon, Sugar (designed for use on the OLPC, the laptop given to kids in Africa, who I doubt have much computer literacy), and more.
While that may seem daunting, and thus complex, it really isn’t. The fact that Ford, GM, Dodge, Toyota, VW/Audi, Subaru, and many more all make cars doesn’t keep people from driving, so who should a wide range of UIs stop somebody from using Linux? And many of them have enough common features, along with all using the same console commands in Terminal, that it’s almost like arguing that the color of the case affects usability or performance. Just like different cars having the same pedal arrangement and steering wheel but arranging the dashboard differently, it’s mostly cosmetic with the differences being more imaginary than actual.
Some of those options are far simpler than Windows could ever hope to be. Many Linux distros get whatever software you want/need from a repository with an interface not unlike iTunes. Most install what you need to do what you want/need to do by default, the only real issue being that some things are renamed. Linux doesn’t have Photoshop; they use GIMP. There is no Internet Explorer; it’s usually Firefox. Word and Excel? No, LibreOffice!
The only real downside (and the major reason I still use Windows) is for hardcore gaming. While Ryzom has a native Linux client, Skyrim, World of Tanks_, and other games I play are Windows-only, and I just don’t feel like setting up WINE. But how many people really do much with their computers beyond surfing, streaming, and Facebook? And any gamer that knows little enough about computers to qualify as “computer illiterate” really isn’t a gamer; gamers know enough to install video cards and configure the drivers, which is more than enough to count as “computer literate”. Those that don’t tend to stick to games like Farmville.
@dappled_leaves This is 2014, not 1994. Considering that many modern Linux distros only require that you know your name, time zone, and native language to install, I think that anybody who cannot handle that really shouldn’t be using a computer… or shoelaces. Autodetect has come a loooong way, so Linux can now plug-and-play about as well as Windows can. The sole exception that comes to my mind being hooking to an iDevice, but given the flaws of the Windows version of iTunes, I don’t see that as a real ding.
@livelaughlove21 You don’t know anybody with a Nook, Kindle, or an Android smartphone/table? Or uses a GPS in their car?
@filmfann I must be weird then. Most of the people I know that know anything about Windows are well-versed in multiple OSs, There may be more people that think they know about Windows, but I have never had any trouble finding people that knew Linux well enough to help me.