Source was great but it was more or less the same gameplay/game. I'm looking towards this because CS got old way quick.
Accuracy was toned dramatically, speed increases, hit registration got worse and is still noticeable on lan servers. Even the hotkeys were different. Ammo purchasing, etc. The list is pretty big. These changes alone made CSS more pub friendly.
The old CS lasted until a year after the introduction of steam. I believe that still outranks WoW.