minusach, are you looking for a walking park? If so, there Amherst bike trail is quite extensive
Link to Bike Trail Map
Niagara County has The Oppenheim Park (broken link) located off Niagara Falls Blvd.
Ellicot Creek Park also located off of Niagra Falls Blvd.
The Buffalo park system is beautiful.
They were designed by Frederick Law Olmsted (http://buffaloolmstedparks.org - broken link)
Here is the NYS park listing
As mentioned above Chestnut Ridge Park is huge and offers much hiking.
If you want a big park, look into
Zoar Valley