My observations on trains I have taken ( I live in Boston )
Lake Shore Limited ( or as my wife calls it the Late Snore Limited ) I have taken numerous times. Boston/Albany section is frustratingly slow for reasons Amtrak can't control but Albany/Chicago is usually fine as long as the train makes its slot window.
Auto Train No Complaints except dealing with Washington rush hour traffic if you didn't get a good night's sleep is not fun.
Cardinal Took it coach from DC to Chicago and only have 2 lasting memories from the trip. How pretty Cincinnati looked at night crossing the Ohio River and not a single credit card transaction was ever billed to me.
Broadway Limited In February 1977 I bought an Amtrak Rail Pass for 30 days for what was a very low price. I was booked to connect in Chicago for the Southwest Limited but wound up spending 2 nights at an Amtrak hotel with taxi and meal vouchers as we were 14 hours late. The 'hotel' I was sent to was the Holiday inn - Midtown at Halsted and Madison which in 1977 was skid row. I didn't know Chicago then and I was dumbfounded that downtown Chicago was so bleak. Then I had to take cabs to the approved Amtrak restaurant which was on N Dearborn and I think it was called 'The Rainbow'.
Southwest Limited Spent 15 hours in Kansas City waiting for the train from NY (National Limited) to arrive as it was a guaranteed connection back in 1977.
California Zephyr Is my favorite train by far. The scenery from Denver west is spectacular. Glenwood Springs, CO is a fascinating stop as the locals are ready to sell you anything
Empire Builder Heading west North Dakota and Eastern Montana are to be kind boring. I was disapointed.
Coast Starlight Took it last week from Seattle to San Jose for work and have been on it several times previously. My sleeper attendent said we are the best LD train in the system as we don't have to deal with Chicago BS.
Capitol Limited A very underrated train.
Downeaster Amtrak in name only but what a wonderful job the Northern New England Passenger Rail Authority (NNEPRA) has done.
Hiawatha When I lived in Chicago I took it often to the Milwaukee Airport for cheaper fares.
The first overnight train I ever took was in April, 1967 with my Mom from Boston to Miami in the dying weeks of the Seaboard Air Line RR and my love of train travel stems from that trip.
The bulk of my Amtrak travel is on the NEC and I thought I would see 2 1/2 hours between NY and Boston in my lifetime but....
This is from 1987