The number one candidate is Tokyo. The world's largest city is also its most dangerously seismic. It sits on a spot where where continental plates are grinding against each other or "subducting" (moving one under another). Most places are major seismic hotspots if they are in a region where there is only one such situation.
There's a "felt" earthquake in Tokyo on average every seven to eight days -- this a metropolitan area nearly twice the size of New York.
Other hotspots would be in China, the Philippines, and near the Himalayas, while in the U.S. Los Angeles is the most dangerous city -- followed by San Francisco, Seattle, and the region from Memphis to St. Louis. Las Vegas, South Carolina, and New York City are also in the "top ten."