I am just about the biggest "Rail-Nerd" known to man (and I'm proud of it) and I go through railroad sims like jugs of milk an I can tell you from alomost 8 years of experiance,
If you're going to get MSTS don't wait until MSTS2 just go get the older one now, I'm sure there kind of cheap.
If your going to go with another go with TRAINZ classics 1&2 because it has more FREE content avalible online for download.
Hope I could help,I own 2 versions of TRAINZ and MSTS
The Lord of the Llamas