Despite was overall disappointing (compared with the rest of the series), something can be still saved.
I was proved myself wrong when I started to play the game. Despite it is a pretty nice game, it lacked of so many things it would be pointless to name them all. Still, here are some things I didn't like.
Industries management is awful: you can purchase industries, but only 3 per station (city). You CAN'T sell them, so, if you made a wrong choice, yuo are stuck with that choice until the game ends.
Rails design is terrible: you can only build rails continuing existing ones. No way to add a piece of rail apart from the rest of the existing network. I did like, however, the way you can build rails with bridges and all that, completely automated. Another thing I didn't like was the steam, diesel & electric management. Im RRT3 you had to electrify a piece of rail in order to use electric trains; here, it makes no difference whatsoever.
The game is too fast: you can go from 1840 to 1980 in less than 3 hours of gameplay at normal speed. Besides that, you only get from 4 to 6 trains per map. Meaning you lack of options when choosing new trains is an important thing for any tycooner.
AI is still clumsy and makes terrible errors when lying tracks on the map, doing impossible-to-understand designs to resources not even worthing it. Of course, these designs complicates your job with your own railroad company instead of getting a big pile of money for the competition.
The maps are extremely small: despite Railroads! uses the Civilization 4 engine, the maps are incredible small. You can get to one part of the map to another one in less than 4 seconds of scrolling. All the maps are same size, and you can't change this. Also, the maps that come with the game are limited and very repetitive.
The difficulty of lying tracks and managing resources is extremely easy overall. Yes, you can control some difficulty options, but they are too basic.
There's no map editor in the game and you can't set the AI difficulty, giving you even less options.
Overall, Railroads! is a fair game, but very far away from being called a "good game". Don't even try to think this game will become a classic, cause it won't, it lacks of every little (and major) detail to make it a classic. Requires too much hardware for the few options it offers.
Recommended for people who want to play a fairly interesting railroad simulation game. Not recommended for the old Railroad Tycoon fan: you'll find this game disappointing and, at least as I think, an insult to the complete series.
If you want to play something a bit more featured you could try playing Locomotion. Or you can get the dust out of your Railroad Tycoon 3 and have several hours of fun thinking you are actually changing the world's direction by managing an army of steaming creatures.