Listed by order of most scenic:
#5 would be your best bet, if you're looking for awesome scenery, especially on the train. Coastal California(Santa Barbara, Carmel, Big Sur, San Francisco, Redwoods) Oregon, Washington, Vancouver and plenty of Canada. Yea, bring a camera.
#3 choice is nice with San Francisco, Reno (skiing & gambling), Salt Lake City(great skiing)and Denver(beautiful Rocky Mountains)with not much after the Rockies.
#4 the coastal portion would be great, don't know Glacier Park or Grand Forks,
#1 and #2 are pretty uninteresting and not much to see other than what the cities offer.
#1: LA, Tucson to Dallas is desert, pretty barren. Think the outback without Mel Gibson aka
The Road Warrior
San Antonio has The Alamo and The Riverwalk, St Louis Arch.
#2: LA to Albuquerque is pretty bland by train. Kansas City has great BBQ. Kinda follows Route 66.
Yea, #5 would be my first choice.