My name is Chad and I hate using linux... however....
Linux has never tried to replace windows for the common user. It's focused on being a useful, security minded, light weight alternative for power users, IT professionals etc...
Linux has never marketed itself as a gaming platform, or multimedia home system etc. There are flavors of linux USED that way, but never advertised like windows. Linux has only recently (past 5 years) reached a point where it is user friendly to new users. Fedora Core or Unbuntu really took off with the whole user experience.
"But there's no content!"... what are you smoking? Sure... your mom can't install "Couponfriend" on a linux machine but that's not what Linux as a whole is focusing on. Linux is a business grade utility. It's a solid alternative to windows that allows you to do almost everything windows can do. The limitations you encounter are what programs you use.
A company I work with recently made the push to move to linux distros instead of windows. Dear lord the users hated it at first until productivity went up, and IT costs went down after 6 months.
There were 567 LESS tickets concerning hacked machines, malware and crashes. The centralized management software they use controls what can be installed on the machine... and pushing installs works just like windows except the machine doesn't have to restart. This solved a lot of issues for the small business as they just couldn't afford the windows equivalents.
The difficulty comes in what programs are being used. Users navigate just like they used to to find files. Hell they even created "My Document" folders... except those are hosted on a SAN, but the user doesn't know.
Linux is NOT dead as a desktop OS. It just might not be at the point of a typical user who thinks Best Buy is a smart place to go for a computer.