I recently took a trip from Chicago to LA and saw some folks doing just this! They had a restored Pullman sleeping car and a kitchen/bar car behind it with crystal chandeliers. Maybe the single most luxurious way to travel. Every stop people would get out and gawk at their cars.
Rail is my favorite way to travel. Going to sleep at night with the country going by is one of the finest feelings imaginable in life, little towns with lights on in empty public squares, just one of my absolute favorite things. And you wake up in endless fields or breathtaking views of canyons and mountains. The people are friendly and you meet new ones at every meal. The sleeper accommodations aren't exactly the Ritz, but they're cozy and comfortable and good for reading or writing or just sitting and looking out the window for hours. Coffee is plentiful and decent, meals are probably microwaved but served on white tablecloths. Cruises give me a feeling of disconnectedness. You're on endless waves, endless sea, in the middle of nowhere. On the train, even going through a desert you feel like you're in the moving center of the world and every stop you could get off and be in a town you'd never heard of that means something to someone. You feel like you're a part of the grand and forgotten history that built the country.
I'm not sure why, other than for the nostalgia, I'd do this other than a trans-Atlantic ocean liner. I have take fairly comfortable sleepers in Europe but nothing like a luxurious ship.