My thinking is that the simplicity of Quake counts for a lot. It's just easier to create a Quake map.

I've long wanted to create a Half-Life 2 map but the learning curve seems daunting to really come up with something cool.

Quake ... eh, some brushes, a few monsters, some lights - done!

I wonder how the Doom community stacks up. 

 

vastly outweighs the other communities, a quick check shows roughly 300 releases in 2015, including plenty of 30+ mapsets. 

Don't count releases. You have to look at the actual complexity for anything meaningful comparison. A release might be 1 map or 15 maps. Vastly different.

Quake and Doom have very diverse possibilities while the HL universe is very limited. Not many things look as boring as HL2 maps to me but I might be negatively biased. 

I tend to get the impression that we're just quake mappers and coders making quake maps and tools and engines for other quake mappers and coders - as opposed to making stuff for a wider public - so our community is kind of self-sustaining now and feeding off each other until the end of time.

We are a perpetual motion machine of quake content creation, and appreciation, and creation...ad infinitum. 

The Doom community is absolutely crazy. I probably should have included it in the list but I don't follow it as closely as the games listed and wasn't sure where to go to find a full list of 2015 releases.

I'm more interested in the question of "what makes these communities so active and fruitful" rather than a popularity contest.

I think Willem has a very good point. The simplicity of creating something for Doom / Quake helps greatly. When you look at the step up in work from Quake -> Half-Life you suddenly introduce heavy scripting logic, and a bunch of other things that slow down development. 

So Doom's popularity comes from a number of sources, but one of the big recent ones is Twitch streaming. Doom speedrunning got a little bit big after one of the AGDQs, and got a lot of people interested. Dime directed people towards doomworld and encouraged people to check out cool new releases and we got a noticeable influx of new members and new mappers. Of course, Doom 4 has helped as well, but that I think will have more of an affect on 2016 than 2015. 

B2B Quake being awesome.

Also without actually reading the original post, HL1 was outclassed and overridden by HL2 in every way, so there would be no need to make anything for HL1 any more. Quake hasn't been superceded by a relevant game in the same style. 

Already mentioned, but whatever:

1. Play style
2. Ease of build
3. Community

I think these are the factors that keep it going.

The play style isn't anywhere else. The only genuinely fast and uncomplicated FPS games on the market are indie procedural lack lustre efforts trying their hardest to be teh retr0.

Maybe you could count Painkiller? No idea if they have a modding / mapping community though.

The big advantage is that Quake is easy to play - you've got directional controls for moving, shoot, jump and mouse look. No alt fire, equipment or loot to piss about with, you just run around shooting stuff. This means even brand new players can just get into the game immediately without having to learn it first.

2. Not only is it easy to build something in Quake, it's also easy to make it look good. It shouldn't need saying, but good != HD. (Although I'm not sure what HD is even supposed to mean anymore).

The techniques are tried and tested, and not particularly difficult to master once you get going. The only real barrier to making an awesome looking level or mod is artistic flair. And even when someone considers that they don't have that, with enough perseverance they can still produce something with its own unique style thanks to how lo-fi quake is by nature.

The latest additions for dirtmapping, fog, skyboxes, better suns, texture packs and so on add a lot here, giving new content creators a head start.

3. The community itself is self sustaining. Not only sites like Quaddicted or func, but also the player centric ones like QuakeOne or the raw data of the various wikis and associated 'frozen in amber' sites, and the blogs, twitter accounts, youtube videos and so on.

If you've got nobody to answer the question 'Why doesn't this work!?' then you're going to get frustrated and give up pretty quickly.

It rarely takes more than a half day before such questions are answered on the mapping/coding help threads. And to the credit of the new guys who turn up, they keep learning.

Finally, a special mention - Trenchbroom had a much bigger effect than many people realized in the influx of new faces - being retweeted by John Carmack (and other influential people) exposed the community to people who otherwise wouldn't have realised it existed.

And the ease of use and quality of the tool doesn't hurt either! 

Is that there are still new faces showing up around here, some of which stay and crank out top notch releases. Who had heard of mfx five years ago? Or Fifth, or Daya, or all of the others who suddenly came out of nowhere and released great stuff? Also sock switching to Quake and releasing a string of incredibly good releases contributed a lot.

I think that the is influx of new mappers with new ideas was had a great impact. Put together with the new and improved tools that have been released in recent years, I think that accounts for quite a bit of the resilience of this community. I sure hope that this will continue, and that we will see more new people in this community cranking out the good stuff. 

I think that Carmack's and Romero's mentions of TrenchBroom, and the RTS article about it, have had a great effect too. I don't believe that it's attributable to TrenchBroom as such, but more to me getting lucky when emailing those guys. And I'm sure as hell going to try again when TB2 is out.