In my experience the most popular and fun “party games” are boardgames such as Top Ten, Time’s Up, Hot & Cold or Codenames (more or less in that order). They work best for 6 to 10 players. Though I don’t think they shine in a highly competitive tournament setting.

Randomness exists in all of these games but I consider it very balanced/smoothed out so it shouldn’t really affect the outcome. Not all of the games I mentioned have permanent teams, but that can easily be changed with house rules.

It’s a nice game, probably one of the best RTS projects out there. It was probably even better 10 years ago. That about must’ve been it’s peak more or less. Maybe a bit more.

I feel like comparing OTTD to OpenLoco is a bit similar to comparing Freeciv to Freecol. OTTD and Freeciv just had so much more popularity and development. But OpenLoco and Freecol are still nice to try.

Of course! TTD and Locomotion were developed by the same person. From my understanding Locomotion is closer to the Roller Coaster Tycoon engine and UI. Also I think I remember reading an interview in which Chris Sawyer said Locomotion had the cleanest code out of the three.

On that note, considering the original engines are similar I wonder if OpenRCT2 and OpenLoco have any big similarities in the code base as well…

Excluding the two games that were already mentioned, personally I find Zero-K and FreeOrion to be pretty high quality open source games and enjoyed both of them. The first requires steam afaik so there’s quite a limitation and the latter is still far from complete, but it was still enjoyable with a lot of interesting game mechanics when I played it.

Some other FOSS games that I consider high quality but haven’t played quite as much so can’t say for sure, or don’t have strong opinions about:
0AD, OpenRA, OpenTTD, OpenRCT2. Simutrans, Unciv, CorsixTH, UFO:AI, Bitburner

Some other FOSS games that I’ve read about a lot and as far as I know are really popular and considered relatively high quality, but I either haven’t tried them at all or find them (a bit) overrated:
Beyond All Reason, Freeciv, Unitystation / Space Station 14, Hypersomnia, Veloren

You wrote that you’re not looking for FPS games. Note that Hypersomnia is a top-down shooter and Veloren is a third person (over shoulder) action RPG. So if you dislike shooters or if you dislike specific camera locations these might not be for you.