It's bloody. It's profane. (Though not as much of either as I remember Black Ops being.)
It's also the most addictive game I've played in forever. It has loads of loot. Open world design. Tons of quests to take on. Character leveling, complete with tech trees and improved performance. More loot (no, seriously, there are probably over a million different guns in the game... sure there's a lot of similarity between them, but the hunt for the perfect gear never ends). Same-console co-op. Online co-op. It wouldn't be fair to call it "Oblivion with guns," but that's probably the closest comparison I can make.
Halo: Reach is also good for all the reasons Drew said.
Best thing about Black Ops is zombie mode. Buuuuuut... Left4Dead does zombies better.
The campaign is definitely the best and most coherent story I've seen in the series (haven't played them all, though), but I ultimately found it less thrilling than Modern Warfare's.
But... Borderlands. Do it.