Railroad tycoon 3 is ok, for us mac users its the only game for OSX. They really need to make an update to work better on the new Intel macs, my macbook pro gets very hot playing. Also, there are a few bugs that drive me crazy, such as trains slowing down to about 2 mph when approaching a station, making a huge traffic jam (it takes longer for a high speed train to make it to the station when slowed down then to travel the distance between 2 cities), when electrifying track you have to extend it about a train length from the station on the other side otherwise your electric trains won't make it to the station (doesnt sound like a big deal but when you have to bulldoze half the city to build your track its pointless), and a very peculiar tunnel issue, where when building track above or near a long tunnel, moving the mouse over the area where the tunnel runs will pull the track up to the surface, creating a very steep grade that will stall your trains traveling through the tunnel. Also, I wish they would allow you to bulldoze grades, almost every other tycoon game has landscape deform tools. Even if they made it cost a fortune and only allow certain depths (or raised heights) this would make building track in very mountainous regions such as switzerland's map a lot easier. Also, it would look more realistic than a track going up a 12% grade in order to connect to a bridge.
One thing that also frustrates me but can add to the excitement I guess is the fact that electrified rail over bridges gets very expensive with maintenance costs or whatever as the game progresses, it will make you go bankrupt even if you have millions unless you buy up a lot of industries. Speaking of industries, I think it makes the game a lot more boring, too easy. Also, I miss having to specify that you want your train to carry coal or coffee or whatever, instead of just being able to pick any cargo. The game's entire industry supply/demand model has gotten very complex.
Overall the game has very nice graphics and is enjoyable to watch, but tends to be very easy at times unless you set yourself up to fail from the beginning. Its a great game for kids