As I am sure you can guess from the title of the game, the whole point of Railroad Tycoon is to build a railroad and dominate your 3 computer controlled opponents. There are several eras in which to play. Most of which place you firmly in command of a railroad during the golden age of trains.
This game is has pretty good levels of "realism" especially considering how old it really is. You can adjust such scales as competition between you and the computer controlled railroads, economics models, and several other more minor scales. You also have the options of establishing different types of terminals for your trains to pick up people and other assorted cargo at various towns.
This game was surprisingly fun considering how old it is. I managed to buy it and 3 other games on one CD for $1.99, so I definately got my moneys worth out of this game. So if you are looking for a fun and nastolgia filled game you should consider this one. However, if you are a graphics junkey I would probably look into Railroad Tycoon 2. Although I have not personally played Railroad Tycoon 2, it looks like it updates and improves Railroad Tycoon.