I've always loved OpenTTD, probably something to do with the way the game looks, sounds, and the deeply (for lack of a better term) autistic* impulse to do the same thing over and over again for no real benefit other than watching a number go up. A quick explanation that is in no way me trying to make the game sound comically dry: in OpenTTD, you manage a public transit company. That's quite literally it; there's a bit more to it, like figuring out supply chains and having to make the expensive switch from steam to diesel to electric trains, but that's it.
If that sounds incredibly boring, then yeah it kind of is I admit it. But it's fun watching pixelated trains go back and forth and raking in tons of money off of exciting things like coal and lumber. Get this, there's oil, too!
* I recently looked at actual video footage of myself as a kid - specifically at my first communion way back in the late '00s - and Jesus Christ. There's a part where I openly glare at the camera guy (who my parents knew) for ten seconds and I keep doing it whenever the camera passes near me. At the start I'm literally rocking back and forth until I notice he's filming me. No wonder my teachers wanted me to get tested.
I think it's worth mentioning that these screencaps are from one of my own games, one that I played with a handful of friends. Some of them sort-of knew about OpenTTD, others hadn't but were interested in finding out why you'd want to play a game where you watch tiny trains go back and forth. The funniest part is that the latter group ended up being amazed at how relaxing the game was. Aside from the vanishingly slim chance that a factory gets bombed by a German plane between the years 1939 and 1945, there's no 'enemy'.
Well, there sort of is. See, OpenTTD is all about cutthroat capitalism. I'm not going to be one of those people who write about, fuck, I dunno, the postcolonial ethos of the music they play at Chuck E. Cheese, but I feel like that's a really fair assessment of the game. It's about running a company and succeeding by any means necessary.
Here's an example: one of the things you can do is fund road reconstruction in a town. This is completely unecessary and has zero actual benefit; roads and rails in OpenTTD don't degrade. A passenger line running between two towns can be a hundred years old and it'll never, ever matter. What this does mean is that another player's buses (practically necessary at the start for getting the money and goodwill needed to do serious shit like bulldozing a neighborhood so you can build an airport) won't be able to run and, as a result, their rating in that particular town will start to plummet.
It's amazing. If Ayn Rand made a video game, it'd look like OpenTTD. Everyone is John Galt.
The game pretty much outright encourages you to fuck with other players however you can. I'll give an example from a game I played back in 2012 (the youngest player was me - 12 - and the oldest was 40.) I've got trucks running to and from a depot set up near an oil refinery just outside of a major city, transporting vaguely named 'goods' to and from. Another player sees this, realizes that this is my primary way of earning money, and builds a circular maglev train running around the stretch of road they have to pass through to get to the refinery.
It crosses over the road at as many points as possible. It goes pretty much without saying that, once that train started moving, my trucks were gone. And the part that I find interesting is whenever a train hits a truck, or it's derailed, or a plane crashes, a little newspaper-esque notification appears at the bottom of your screen appears saying how many people died. I had to click through about ten of those saying that some poor truck driver was splattered by a sci-fi train going 320 mph.
Another thing that I find interesting (and frankly love about it) is that the world of OpenTTD is eerily empty. At the start of the game, there's nothing except a few dozen disconnected towns with between 50 to 5,000 people in them. There are no roads connecting them. Industries do not function. The lights are off, food isn't getting to grocery stores, and it's getting cold.
So in a Randian twist, you are completely necessary. OpenTTD answers with beaming optimism 'who would build the roads' in a hyper-libertarion society. The oil barons who own everything, duh!
That's probably why watching the weird, empty region you start with grow into a complex chain of interconnected cities, all with functioning industries and running supply chains is so satisfying. You did that. No one else did. Okay, maybe another player was mostly responsible, but you probably helped. That's the big lake we all decided to set up around; in 1960, the year we started, it was more or less a desolate collection of small towns and farms with zero chance of growing. By 2006, the date we decided to call it quits, the whole region was bustling and we had passenger lines running from one end of the map to the other, passing through dozens of other towns and cities.
Basically, I love the game because the numbers go up.