I have played neither of the originals or the open source ones but I really liked Factorio and building traffic in city-building games (even though I feel they're too limited). Which one should I spend some time on, OpenLoco or OpenTTD?
I have enjoyed Simutrans, where passengers have desired destinations and use your service if you can take them there. They can change between different transports too. This often creates choke points. For me, that makes the game interesting.