The first train I ever drove was Acela on the Northeas Corridor, and I say that this and every route has detail and many of the objects are one-of-a-kind (an object that you can only find there!). Probably the best out of all of the routes is the Marias Pass route. You can run through the Rockies, and speed through the flatlands near Shelby, and you soon find out that Montana isn't just beautiful moutains!
In addition to the wide variety that they have already gave you, there are thousands (maybe even millions) of free ad-ons online, including engines, freight cars, activities, cabviews, sounds, and even routes! Just type in "Microsoft Train Simulator" in your browser and you get thousands of results!
If you don't have enough time to buy a new route online, you can simply make you own! Included with Train Simulator is "Editors & Tools", where you can make your own routes, and even convert default objects into your routes! Editors & Tools also lets you make your own activities for your new routes, and you can even make custom cabviews for more realisim in some engines!
I believe that this is the best train computer game ever made, and you soon will too when you buy Microsoft Train Simulator, and, best of all, if you want more, you can find exatly what you want! Probably there are more add-ons available for Train Simulator than any other game.
But none of this great fun happens if you don't buy Train Simulator, so get it today! And when you do, you can sit at you computer, start up your train, and ride down the tracks for many years to come.