They've been mentioned twice before, but once more won't hurt. The pop stuff is great, but under NO circumstances should you miss out on his gospel recordings with the Soul Stirrers:
Sam Cooke with the Soul Stirrers - Specialty 7009 (includes some early pop sides also)
The Soul Stirrers: Jesus Gave Me Water - Specialty 7031
The Soul Stirrers: The Last Mile of the Way - Specialty 7052
This music is classic, great, beautiful - whatever word you want to lay on it. And you don't have to be religious to be moved by it. Try one of these and you'll be listening to it for the rest of your life.