Avoid the bus tour at all costs. A horse ride is an incredible way to see the pyramids in relative isolation. Indulge in your Lawrence of Arabia fantasy by galloping past ancient stones. It takes a few hours but you get to see the Pyramids at angles normal tours don't get to experience.
Many of the stables mistreat, underfeed, and beat their animals. So if your booking through your hotel ask which company they use. Also avoid the camels as the desert is hot and they are very slow.
FB stables has a good reputation from many reviewers on trip advisor +20 (0)106 507 0288.