There is a reason why people call the PC the "master race" of gaming platforms. It was born in 1981, and has been evolving constantly since; its longevity, ubiquity, and lack of central approving authority gave it the most incredibly vast library of any system, ever; hell, it has become so immensely powerful that it has hijacked what was once a generic term ("PC" meant any personal computer). Now, about that library thing... since there are dozens of thousands of games, it would be impossible to keep all recommendations in a just few pages. This motherfucker has to be split in several pages, each encompassing an "era" of PC gaming (mostly related to each succeeding version of Windows, but not strictly so).
If you're having trouble making old games run on modern systems, be sure to check the troubleshooting page.