Great question! The Cyclone at Coney Island in Brooklyn, New York gets my vote. Since 1988, the infamous Cyclone is listed as a New York Landmark--it's that special a ride. The compact wooden twister goes 60 miles per hour at top speed and the ride time is one minute, 50 seconds. Whoosh!
Here's some info on Coney Island:
Located just a 45-minute subway ride from Manhattan (on subway B, D, F or N to Stillwell Avenue), in south Brooklyn, Coney Island is a popular haunt for New Yorkers and tourists alike, because of its stretch of beach and historical amusement parks. Major attractions include the New York Aquarium, Surf Avenue and West Eighth Street (tel: (718) 265 3400; website: www.nyaquarium.com), located halfway to Brighton Beach. The Aquarium is open daily 1000–1630. Its Aquatheatre is home to dolphins and sea lions, the Sea Cliffs Exhibition, features walrus, penguins and giant Pacific octopus, while Discovery Cove is an interactive entertainment complex for children.
Coney Island’s amusement area comprises several amusement parks, featuring the Cyclone roller coaster and the Wonder Wheel, the tallest Ferris wheel in the world. Many visitors partake of a Nathan’s Famous hot dog on the boardwalk – a seaside treat for generations (see my review of Nathans).