What is the closest hotel to the falls?

Closest is the Sheraton Fallsview Hotel, literally right across the street from the Fallsview area. You can see the Horseshoe Falls from some rooms, but the real "closest" title goes to the Marriott Fallsview—it's basically on top of the brink, with some rooms having a direct, unobstructed view of the water. Both are walking distance to the Fallsview Casino and the main tourist strip.

That said, if you want the absolute closest to the actual water, the Oakes Hotel overlooks the Fallsview parking lot but has a direct path to the Table Rock observation area. Prices are brutal in peak season—expect $300-600+ a night for a view room. For a budget option, the Days Inn by the Falls on Ferry Street is a 10-minute walk but way cheaper.

My take: unless you're dead set on a room with a direct falls view to fall asleep to, save your money. The view from the public promenade is free and better than any hotel window. Stay a block or two back and use the cash on the Skylon Tower or a Maid of the Mist boat ride instead.