For a lot of trips, Amtrak is about the same as flying. Looking at a round trip from NYC to Chicago, on the arbitrary dates of March 26 to April 9, Amtrak costs $180 while Kayak shows the cheapest flights at $159. Of course, Amtrak takes much longer (20 hours) but is less hassle, and at that price the flight only lets you take one carry-on while Amtrak lets you bring two checked bags and two carry-ons. Adding checked bags will add $60 for the first and $80 for the second. Amtrak is also better for the environment if that matters to you, and the price difference is about the same as the cost of the carbon offset for the flight.

Overall, choosing Amtrak or flying is perfectly reasonable in different situations. Amtrak could definitely be improved a lot though!