Canada's VIA rail trains are really nice. The commuter line between Windsor and Toronto (TO) is uneventful, punctual, and there is a heavenly blue sky with white clouds painted on the ceiling of every car!
Every American should have at least one Amtrak adventure, though ... Amtrak is a very strange beast. As a young 'un I was dragged on many miles of Amtrak'd lines, thanks to my mother's fear of flying, through all parts except the deep south/south central. It's succeeded in changing its image in Southern California - the trains running between San Diego and Los Angeles are beautiful, clean and spacious, and actually classier than the Metrolink commuter trains, which aren't so slobby. And the Krispy Kreme donuts are a big hit with passengers. They manage to attract business travellers and tourists; it may actually be profitable. Unfortunately they just don't know who their customer in the rest of the West is anymore - is it the person who's trying to save money, or the retiree or tourist who wants to see the country at a leisurely pace? They try to do both on the longer lines and fail miserably.
It's pretty crappy trying to sleep in the coach seats, but they also allow a chance to get to know some of the other passengers. I don't know if they still do this, but as recently as 2002 they had packets describing the sights on the Coast Starlight (Portland-LA), and in the 1980s and 1990s the Southwest Chief (Chicago-LA) used to bring guides on board the observation car, to narrate parts of the journey, with expertise in either Native American culture or the desert environment.
Chicago's train station is usually considered an architectural gem, particularly the large waiting room (I've added an image to the bottom). I travelled through there a lot through the 1980s and 1990s, and hazarding that if it came off as seedy, rather than bustling, you might have arrived either on a weekend or after hours, as there's not much going on at that time of day.
During the week there are tons of commuter trains, and more downtown workers visiting the shops and eateries, and the Art Institute's collection and other museums are within walking distance. A lot of the major Amtrak stations are like that, like Washington, LA, Boston, San Diego - the bottom level or one section is rundown, but another section has art deco or classical design, access to commuter lines, shops and businesses.
Amtrak could improve their image simply by improving the last few miles of trainyards and their tributaries in most localities. It's hard to get excited about a city when you hear the conductor announce the last stop - you look up and it looks like you're entering a Superfund site.
Chicago's trainyards look especially awful and the Amtrak entrance makes me think of the oppressed worker scenes from "Metropolis"; the last miles going into LA's Union Station overlook the graffitied aquaducts. Actually, it's where "Grease" and many other TV shows and movies have filmed (most recently "Boomtown"), and LA's old City Hall (aka the "Dragnet" headquarters and home to "Superman's" Daily Planet on TV) is nearby, but it tends to freak out tourists.