CS before it went downhill. Played so much de_dust (before de_dust2 became popular) from the beta days to 1.6.
When did it go downhill? I thought CS: Source was great fun. Didn't really care for CS:Go
In 2007, DirectTV killed the North American professional CS scene by pushing CS:Source into their televised CGS league. The top pro players all left the 1.6 scene for 30-40k/yr contracts to play in CGS (a no brainer)... most of them openly hated the game while playing in this league too. The 1.6 scene in the US was still large and active, but never the same. Teams in Europe, Asia, Brazil & elsewhere continued to play 1.6. After CGS folded in 2008, global competition sort died off and many of he top NA players retired. There weren't many NA 1.6 players good enough to keep up with European pro teams after about 2010.
Imo, CS was an incredible scene from like 2000-2008. CSGO has enjoyed a great run from like 2013-2018?. It's definitely lost steam from the battle royal shooters (PUBG & Fortnite), and now Valorant infringing on it's player base. Valve hasn't really been very active in its own competitive scene, which may also be hurting.