Hi Jenrick,
There is a bit of choice nowadays when getting into train simulation. People still use the venerable Microsoft Trainsimulator (albeit mostly heavily modded) as well as the various iterations of Trainz. N3V will be putting out a new version of Trainz, called Trainz: A New Era (aka TANE)which is supposed to have better physics, better graphics and better building tools.
You could also go the route of Trainsimulator 2015, a train sim from DoveTail Games (sold via Steam). It offers quite a few extra routes and add-ons as DLC and is well ensconced in Euro rail (primarily UK and German) although does have a decent North American content list too. Graphically this is a fantastic sim. If you are concerned with the costs, DTG often puts their catalog up for lowered sales prices from time to time (usually anywhere between 20 and 50% off the retail price, but I have seen 75% and 80% in the recent past as well). The editor is comprehensive and there are lots of community made routes, stock etc. available.
The last one I would recommend is Run 8. Run 8 is a train sim that is very accurate in detail and physics, has a nice level of fidelity (but quick to get the hang of although hard to master) that has the added delight of multiplayer. Multiplayer with a group of dedicated train afficianados is brilliant. Note that Run 8 currently is American rail with their routes in California-- the Mojave Subdivision, Cajon Sub, and Needles Sub-- each route is connectable and it is very accurate. Lots of community support is available.
Hope that helps,
Kind regards,
Dave
Currently dabbling in;
WOTR/BoF, Naval Action! also Run 8,
IL2BOS/BOM
"Once again we have failed to die."-- old naval toast