even though i am now modeling the SP, my favorite is still the Union pacific.
why? you may ask....
well, the UP is never afraid to try something new. just look at the double diesels, the turbines, and the massive steam locos. then, there is their active steam program. plus, i dont think anyone can point out another class 1 that willingly gives away locomotives and rolling stock to museums, or one that preserves it's history like the UP.
then there is their beautiful set of preserved passenger cars. ones not reserved for executives like all the other railroads, but ones that you and me can ride in.
of course, there has to be a second place, and it is the Southern pacific. they conquered the west and went afraid to try new things while doing it.
third would be the Chicago & Eastern Illinois Railroad. my dad worked for them as a kid and thats what got me interested in them. once i did a little research i found it to be a pretty interesting railroad. so now i spend all my time whining to manufacturers to get them to make more C&EI locomotives and rolling stock.