Since Walt Disney World covers 47 square miles, if proximity to the Magic Kingdom park is important to you, you'll want to stay at one of these resorts:
Contemporary Resort including Bay Lake Tower
Polynesian
Grand Floridan
Ft. Wilderness Resort and Campground
Wilderness Lodge including the Villas at Wilderness Lodge
All of these resorts have boat transportation to the Magic Kingdom.
The Contemporary Resort is the closest hotel to the Magic Kingdom as it is actually within easy walking distance to the gate.
The Contemporary, Polynesian and Grand Floridian are all on the Magic Kingdom monorail loop.
The Wilderness Lodge and Ft. Wilderness also provide bus
transportation to the Magic Kingdom.