This balance made Counter-Strike a trailblazer (along with Quake III) for online competitive gaming organizations such as the E-Sports Entertainment Association League. Players formed teams, usually called clans, to practice in scrimmages against one another in hopes of landing that ever-elusive CAL-i invite (a now-defunct invite-only pro league, which was basically Counter-Strike's NFL). Many legends were born through the game, too. Though Johnathan Wendel (who goes by Fatal1ty in the professional scene) got his start in Quake III Arena, he became a feared Counter-Strike legend, and many strived to gain similar recognition. Some, such as Kyle "ksharp" Miller and Patrik "f0rest" Lindberg, even succeeded.
Of course, Counter-Strike did evolve over time, as Valve released the updated Source and, later, Global Offensive versions, which provided a visual overhaul for the series in addition to minor gameplay tweaks. These updates ruffled some feathers within the community, but many adopted them due to the fact that Valve hadn't tinkered much with the underlying mechanics that had made the game so appealing in the first place. And, because Valve didn't overwrite any pre-existing code when these projects were launched, everyone who loved Counter-Strike could continue playing whichever version they preferred. You can still hop into a 1.6 match nine years after its release to experience a familiar glimpse at the game's earlier years.
Perhaps Counter-Strike's greatest achievement is that it's a testament to what the modding community is capable of. It did, after all, begin as a mod for Half-Life--a mod that Valve later purchased the rights to and developed into a fully realized game. There were even mods within the mod. Counter-Strike is where the popular Gun Game mode was born; there were player-made "Protect the VIP" modes, and tons of user-generated zombie survival games, which went on to inspire Valve's Left 4 Dead series.
Even now, the Counter-Strike community continues to expand as more and more mods are introduced. Owning a copy of any version of the game means you have access to tons of player-made ones--and who knows which of these will be adopted into full games, or inspire new modes in already-popular shooters?
Counter-Strike is undoubtedly influential, but it's also one of the most intelligent shooters ever designed. It has incredibly tight and balanced gunplay, amazing map composition, and supports one of the largest modding communities out there. Sure, it doesn't have fancy unlocks or a score-driven economy--but the fact that it still has a substantial playerbase 12 years after its inception says a lot about its design. It's a game that refuses to adopt the trends of its competitors. Much like its community, Counter-Strike is resistant to change. That's fine with us. It doesn't need to.
"Why _____ is one of the greatest games ever made" is a weekly feature that goes through GamesRadar's list of the 100 best games of all time and highlights different titles, explaining why they're on the list, what makes them so amazing, and why we love them so much.