I must say that I loved all the maps that came with Black Ops (and those that came with its DLC), I liked most (if not all) maps from World at War. Modern Warfare 1 had some great maps at its time (although several looked alike), Modern Warfare 2 had some nice maps (some focussed too much on verticality but still fine).
From my point of view Modern Warfare 3 had the worst of them all, closely followed by Black Ops 2.