As a kid i allways liked trains myself, but there was never a lego train, as my dad liked the marklin trains and we used the available space and budget on that. Obviously i - for lack of a better term - raised my kids (twins) to like trains as well and started with duplo trains at 2yrs old, thomas the tank engines and had huge discussions about adding chuggington as well. (the parents won this round) 
Finally, they are now almost five years old and they are old enough (I lost patience) to play with regular lego trains. I bought two second hand sets, 7939 and 7938 and some extra track and every weekend we lay down the track throughout the house and play with the trains. usually my son drives the freight train and my doughter operates the passenger train, that for some reason crashes into the freight train quite often. but we have a lot of fun. 
After a month i decided i need a dad train and bricklinked myself a blue modified version of the emerald night.  During the days we put it together and i was waiting for the parts to come in, he would get up every morning inquiring if the steam loc was done yet, so obviously the first test run was quite a happening. I  and put in an S-brick, wich is a bit of overkill you might argue, as i only need one channel proportionally and a light switch. Why then? Well, my son found out how power functions works and regularly hijacks a different channel and rides off with your train, that's why. At least this way i have some control over when he rides the blue train.