Popularity of FPS Games
First person shooting games are too much popular compare to any other category. Millions of players are playing many FPS games online with each other. Those games with multiplayer support are more better then offline versions. Almost all games are supporting offline campaign with multiplayer for everyone. Counter Strike is best for only online game play.

Players team up against each other in multiplayer game and fight for achieving many targets like killing all opponents. Offline campaign includes single player or team missions to destroy a target, or capture some place. These game players feel like they are in real mode and on war. Almost all games provide great HD quality and use of weapons is like real game play.

Famous Series of FPS Games for Pc
Many game series were too much popular with time and that why their developers are making more in series. Call of duty is one example and one of top class most popular game which is no available for mobiles. Battlefield, Counter Strike, Doom, Far Cry and Borderlands are very popular to play. Games of Tom Clancy’s are more popular then any other games in any categories. They made many series of FPS games like Rainbow Six, Ghost Recon, Splinter Cell, HAWX and Division.

Its not possible to mention all game series and many games which are famous but not in series. Operation Flashout is another example of best FPS game. PUBG is latest FPS game which is available on mobile and pc as well. This is game which is most played these days on mobile and its total action in multiplayer. There are over 10 games in Fallout series which is about future where its apocalypse time after destruction by nuclear attacks. Over 15 games are available in Arma series and each one is better then previous.

Few Lists by Famous Websites
Few top sites provide a lot of similar lists and they add 15 to 25 games in their site. GamesRadar is one example where they add 25 games in their site and provide one of best list ever. VG27 added 50 games from past to future and their choice is really awesome with great collection of games for FPS. 30 games are added in collection of The Gamer site with screenshots and little details. One article was written on IGN which provide best top 10 list of games and few of their games are part of our list too. Providing lists of other site is very important for you to show that we are not copying anyone content. Almost most of entries in our lists are unique and article written are perfect for everyone.

Short Summary of Best FPS Pc Games of all Time
Call of Duty – Modern Warfare (2019)
Counter Strike – Global Offensive (2012)
Tom Clancy’s Rainbow Six Seige (2015)
Far Cry 4 (2014)
Battlefield 3 (2011)
Left 4 Dead 2 (2009)
Arma 3 (2013)
BioShock (2007)
Wolfenstein 2 – The New Colossus (2017)
Half Life 2 (2004)

read more details here
https://top10listss.com/best-fps-pc-games-of-all-time/

What were the criteria for making the top?

It seems to me that cs go is much more popular than described in this top. Basically, modern FPS games are popular only for the first time after their release. Cs: Go has been the most popular game for eight years now, I think this is an excellent result. Recently a new game in this genre was released - valorant, but it was popular only for about the first two months, then it began to lose its popularity due to the fact that cheaters began to appear there. For some reason, cs go does not lose its popularity due to cheaters. CS: GO was one of the first games to introduce a system of cases and skins. It's very difficult to get some cool skin in the game itself, so I use services like https://itemherald.com to get a cool skin. I think cs go will not lose its popularity for many years to come!

Octopus3000:
It seems to me that cs go is much more popular than described in this top. Basically, modern FPS games are popular only for the first time after their release. Cs: Go has been the most popular game for eight years now, I think this is an excellent result. Recently a new game in this genre was released - valorant, but it was popular only for about the first two months, then it began to lose its popularity due to the fact that cheaters began to appear there. For some reason, cs go does not lose its popularity due to cheaters. CS: GO was one of the first games to introduce a system of cases and skins. It's very difficult to get some cool skin in the game itself, so I use services like https://itemherald.com to get a cool skin. I think cs go will not lose its popularity for many years to come!

I totally agree with you. Millions of people play this game every day. it is very difficult to lose such popularity!