[enra]

Team Fortress started as Quake1 mod, which then Valve made to a Half-Life mod TFC, and later as the TF2 [1]. Also Counter-Strike was a mod as well which again Valve made official versions of.

I started with the Quake TF and now still pay TF2 sometimes. Basically been playing the same game for ~20 years.

1:https://en.wikipedia.org/wiki/Team_Fortress_2#Origins_and_ea...

[Insanity]

Some games are just good so you can play them for a long time. As long as there is a community. I occasionally fire up HL deathwatch and have people playing. Plus CS:S is almost 15 years old and that is quite active (surf communities anyway)