I still play 1.6 around 2-3 times/wk. Actually prefer it over CSGO or Source considering how messed up MM is with Valve going all supernova with banwaves > Steam Sale w/ CSGO @ $7.50USD > Kids hacking > banwave > repeat previous steps. And source, it's like everyone is using modular wallhacks which unfortunately cannot be detected by VAC.
So yeah IMO 1.6 > CSS > CSGO. Don't even know what happened to Condition Zero hah