A lot of train sim are about building the rail network, where Running Train focuses on driving. The scenery (dozens of kilometers of japanese railway) is beautiful and it reproduces the japanese railway system realistically.

I play Euro Truck Simulator 2 (ets) and its my happy place, its just zen, Sometimes i will have a plugin that will get me local radio stations and i will cruise through italy and greece listening to talk shows in languages i don't understand, sometimes i will do it listening to the rumble of the truck, and i switch off, and allow my thoughts to run free.

I've recently started getting into flight sims, and i'm looking for the same sort of thing with that (the only problem with ets is the graphics still looks like a 2013 game) and i think i will get there, its just i'm at the 'learning to fly' stage, and thats kinda difficult. Well, actually flying is surprisingly easy, landing is the tricky bit ;-)