It's still the only game I play.
Got HL, H2, Unreal Q2 etc but only play those out of boredom when there are no-one on the servers cause of the time diff.
It may not be considered mainstream popular and the timing of CTF may have kicked a fantastic add-on in the balls (WOS) but in addition to what Lithium said, it's the close knit community that will keep it going....for a while longer anyways.
I salute too many ppl to mention, you know who you are, your the one's keeping this thing alive.
BTW - check out doomworld.com for christ sake, even that sorry old bastard is still alive, too a degree