Windows is "bad" because its the current leader and everyone hates Microsoft because of all the money they've made.
Don't listen to all the hype. Windows isn't that bad - if it was, it would be gone.
Mac and Linux are the two biggest "Others" out there against Microsoft Windows.
Macs can be limited in scope but would honestly support 75% or more of the average home users' needs.
Linux requires more technical know-how, plus some time downloading programs for what you want. The problem here is that the Linux Programs aren't as widely known as Windows Applications.
Mac's do well because they appeal to the female population since they're cute.
They're good machines and all but limited depending on what you're doing.. They can be pricey and not as many people out there support them as do Windows.
Linux will require some time to download if you want it for free. First, you need a working computer to download it, then you'll need some extra time to install, configure, etc. Unless you buy a Dell with Linux pre-loaded and working. Might be the best option for someone who doesn't really want to deal with it or have the technical background.
There are plenty of Linux users who dwell around here who can better answer your Linux questions, or venture down to the Linux section and check it out.