There's plenty of military commanders who had smaller armies, unfavorable tactical situations, and still emerged (consistently) victorious. That's why it's hard for me to put Lee in the top 10, given his unforced errors cost his side battles and ultimately the war.
At defensive warfare? Lee was superb. He made the best with what he was given, no question; and did better than most.
On the Confederate side (and, indeed, the whole war), I think Jackson was the best General in both tactics *and* strategy. As Deet mentioned: had Lee listened to him more, they might even have won.