Reply #11: There's an FAQ for you (I'm impressed that this exact question is addressed)

[MrCoffee]

Q: I'll be in New York City and would like to visit Niagara Falls. What are my options ?

A: New York City is 406 miles from Niagara Falls. By car it's a 6.5 hour drive.

By plane it's a 45 minute flight (airtime). But from terminal to terminal check-in and check out it will usually take three-four hours (with no delays!).

The train ride is great, the ride is 8-9 hours long and costs $58.00 each way. Usually four departures daily starting at 7:00 A.M until 4:00 P.M. Amtrak offers service from Penn Station in Manhattan. Visit Amtrak's website for more details.

Greyhound offers bus service to Niagara Falls. This route takes 9-11 hours and the fare is roughly $55.00 one way or $105.00 round trip. Many departure times are available but the ride is exceptionally long.
http://www.niagarafallslive.com/Frequently_asked_questions_about_Niagara_Falls.htm