IGN writes: "There are a few genres that the PC platform has dominated throughout every generation as thoroughly as it has with shooters. It's true that Halo popularized the console shooter and encouraged publishers throughout the industry to embrace the gamepad-driven profitability of the genre, but there's still no substitute for the old mouse and keyboard when it comes to indulging in a little first-person awesomeness.
With so many titles to choose from on the PC, we've decided to limit out picks to games that were released since 2005. That meant we had to leave off many of our favorite shooter games from previous years, but it's a testament to the strength of the genre that we still have so many amazing games to choose from. As for what it means that they're all cross-platform titles, well, that's a subject for another day".