The most important question though is if I left my [place of residence] when would I arrive at [destination] and what would my total cost be? Is the airport an hour outside the city and a $50 cab ride? How many HOURS do you have to show up to get on the plane? Taking luggage? Add another half hour minimum to your trip. And not to mention the fun security theater of the airports.
I drive from Boston to Toronto and it is faster door to door than flying and is a much better experience. Chicago from NYC would be longer at 13 hours so flying would be faster. Busses need to compete on other things. Treating you like a human, having wifi and power jacks. perks like ipads on the bus, free books, or gut half the seats and setup poker tables, video games. A bus that is made up of half beds. Themed busses, something, anything to make it more then just a bus trip, something you could charge much more than planes and people would want to use it. Go after a different market then who is currently riding the bus. Charge $500 for a bus ticket and think what you could do provide for that overhead.
Maybe someone like Megabus could do it profitably, because they have some economies of scale and existing capital equipment, but I'd be really surprised if a small-time operation running a single Chicago<->NYC bus were profitable.
Their rapid expansion across the midwest and east coast makes me think Megabus will likely offer soon a way to get from Chi to NYC. Perhaps the trip would take as long as the greyhound trip, I don't know. But its worth keeping an eye on. They have seemed to add routes about every 3 months or so. Connecting the midwest to the east coast would seem a natural progression.