The best option for internet in rural areas depends entirely on the exact location. Cable and fiber-optics will always provide the best stability and usually the best speed where it's available. However, it could be hard to get in remote areas as the infrastructure doesn’t exist.
The next best option is DSL, which uses existing phone lines and is available in most areas that have access to them.
Fixed wireless is also an option which can compete with DSL in terms of performance. However, this depends on the tower's proximity and whether anything interferes with the signal.
For the remotest locations without phone lines and only limited cellular coverage, satellite is the best choice. It can be costlier and slower, but satellite coverage can be delivered anywhere.