Ozzie, I may be wrong, but the only real on-airport hotel at JFK used to be the Hilton. A lot of the other "airport hotels" as advertised in the OAG hotel guide are up to 30 miles away in Queens or Long Island (whichever one JFK is not in. Actually I think it's in both!)

In years gone by I have stayed overnight in-airport: sleeping on the benches in the departure area. Fine until they start Hoovering up around 4am. I wouldn't recommend it during the day though!