Longmen - Y - haven't been to any of the Chinese cave sites, but the photos of the Longmen one have amazed me the most
Yungang Grottoes are the best preserved sites in China with 53 caves containing over 51,000 stone carvings of Buddha and Buddhist. constructed between 460-525 AD during the Northern Wei dynasty.
There are over 2100 niches, more than 100,000 statues, some 40 pagodas built by Northern Wei Dynasty and Tang Dynasty style in Longman Grottos.
However, undoubtedly the best is Magao which represent entire Chinese Buddhist grotto style. It has largest, oldest and the best-preserved Buddhist grottoes.
Magao has 735 caves, with murals covering 45,000 square meters and colored clay statues 2,415 square meters. It began in the period of the Sixteen Kingdoms (about 366 A.D.), and the endeavor continued through the later dynasties, including the North Dynasty, Sui, Tang, Five Dynasties, Western Xia and Yuan.