As someone who used to work in the video game industry I'll give my 5c quickly that hopefully people can use as a good judge as to which to go for.

Rail Simulator is the best for graphical appearence, and with the new updates behaves realistically enough, but lacks new content at the moment, with around 4 loco add-ons including Class 66 and 158. Needs a relatively powerful computer.

MSTS has fairly poor graphics by todays standards but not the worst. It does however behave fairly realistically although, like Rail Simulator, it does not provide things such as TPWS so can lack realism. It does have almost every route, locomotive and stock you could ever dream of available for it by now though thanks to sites such as UKTrainSim (charge a small fee to download) or elseware for free.

The other simulators in general tend to be the worst graphically and have fair to moderate amounts of add-ons available (but not as many as MSTS) - however they generally provide the most realistic and difficult driving simulator, so IMO they cover a neiche market. I've not played every one though so I can't say that for certain of all of them and as such this is a bit of a blanket statemnet.

Either way my sim of choice right now is Rail Simulator.

There is a completely free train simulator called BVE, which stands for 'Boso View Express". Originally Japanese based it has become very popular and there are now many routes and trains from all over the World.

A good website for those interested is TrainSimCentral at

http://www.trainsimcentral.co.uk

There are three versions: the basic one is BVE2, more complex BVE4 and now an Open BVE for developers.

I run BVE2 on my computer, but it is limited to cabviews and forward movement. The signalling systems are however very realistic and the train simulation, speed, braking, acceleration, adhesion and so forth quite excellent.

i got to disagree with all of you 'kujus' 'rail simulator' is one of the best you can get with some amazing add ons you cant get on MS train sim,ive played both and would favour rail simulator
1:you can look round cab not just with no side-to-side views like in msts.
2: because msts has not crap but the graphics are not as good as rail simulator.
3:msts has no passengers at station on rail simulator it has passengers at the station and they move!.
4:msts does not open doors when you stop at he station rail simulator does and makes the beeping sound as it closes!.
5:msts graphics are not exactly good but rail sim has very very good graphics and the detail is unexplainelbul.
6:there are many more things i could go on about but i cant be arsed.
so the conclusion is in my review get rail sim!

Just adding my twopenn`orth. I got Railworks for the PC for my birthday, I`ve had MSTS for a while. In my opinion, the graphics in Railworks are superb, even though you need a decent video card to run the game. The steam locos especially are exceptionally realistic, plus the sounds are good too. There are already add-ons available at uktrainsim.com, and new stuff is being released too. I can see this one setting the standard for a while. Has anyone else on the forum got it yet, and what do you think of it?
Regards Mike.

I use MSTS, and while the ADLs aren't available for it (:p), it's still a great and easy to learn simulator.

I use msts too.
I like the look of railsimulator though.

We are now in 2010. What is the best up to date software?
Regards
27vet

The best train sim belongs to EWS but its a bit to big to nick :D :D :D.
ccmmick.

i have ms train sim works very well i have some nz add ons free where and very good one section is where i drove trains

hi
this is what i think after using these sims for many years ( and developing on them)
Trainz: not best graphics, not very real and best for playing trains not simulating them.
MSTS: not best graphics, rather simple, good addons, decent sim.
Railsim/Railworks: Best graphics, easy to use, great addons, great sims.
BVE: the most accurate game (used by london transport museum), free (even better), cab view only, the only sim to have full alarm systems.
Rail3D: rubbish graphics, decent sim, hard to use.

hope that helps