He was a deeply devoted Christian man, well respected even by the Union. After Lee's army invaded a northern town, and Lee rode into town, a woman was heard to say, "I wish he were ours." Grant and almost all the Generals in the Union respected him, and feared him in battle due to his tactical genius. Lincoln thought so much of him that he offered him command of the entire Union army when the war began.
Lee would not even refer to the enemy as "the enemy." He called them "those people." He never sought glory for himself, he had no vices, and he personal and professional behavior were beyond reproach.