Counter Strike is EXTREMELY popular on PC. At the time of this post there are 590,000 people online playing the Counter Strike: Global Offensive (and that's 1 PM EST on a monday - far from peak numbers that you'll see in the evenings and on weekends). That number also goes up if you include the other Counter Strikes (Source, 1.6, etc.).
Consoles have some really popular shooters, but outside of COD and Halo (which is Xbox exclusive) there's not much of a consistent audience for them. Battlefield is just as popular on PC as it is consoles.
You always have to keep the PC mega-giant games in mind when remembering how popular console gaming is. Xbox Live has 39 million active users as of a few weeks ago. League of Legends - the most popular game in the world, and also PC exclusive has an estimated 90 million active users. That puts League of Legends as about as popular as Xbox and Playstation combined.
Steam has 65 million active accounts. Consoles get all of the marketing and hoopla, but the PC giants of Dota, League, Counter Strike, WoW, etc. all pull absolutely insane numbers of players in consistently month to month.