I agree with Bob Dylan and Neroden that the Sunset Limited wins the "no love" contest, hands down. However, I was thinking just a week ago about how senseless the current state of the Sunset Limited is.
To paraphrase what I said on this forum a while back, the Sunset Limited from LAX to NOL would be a very successful train in any sane world (and I'm not even talking about restoring the train NOL-FL). If you count Phoenix, the SL serves 4 of the 7 largest cities in the U.S. The route also has many retirees who have more time for train travel. Some of the places the SL serves (like Tucson, El Paso, and Palm Springs) don't have the best flight options, making it easier for Amtrak to be a competitive alternative.
Yet the Sunset Limited only runs 3 times a week, serves San Antonio at an ungodly hour, and annoyingly bypasses Phoenix and Las Cruces. If the UP was cooperative and Amtrak was aggressive about improving the SL, there's no doubt in my mind it could be the most wildly successful of the "transcontinental" routes. I'm talking you could easily get a solid ridership base for a twice-daily train, and I wouldn't say that about some of the other LD trains.
I'm afraid the wasted potential of the SL is just a microcosm of the wasted potential of the whole system.