The major difference between this game and the new Medal of Honor is the narrative presentation. Medal of Honor is fairly straightforward, gritty even, allowing you to play different aspects of one single mission within a much larger war. Also, with Medal of Honor, while there is an ultimate mission goal, it is clear your allegiance as a character is to your fellow soldiers rather than to being a "save the world" hero. You feel closer to the action.
COD: Black Ops has different ambitions, as one might expect from this series. As you can tell from the title of the game, you play as an operative on secret, behind-the-scenes missions. The setting for this game is the Cold War - the game begins in 1961 and I believe you play through several real-world conflicts, starting with the Bay of Pigs. I'm only a couple of missions in, so I don't know how far through history this game goes.
I like the type of game that fills in the holes of history. Games that allow you to play through a story that is framed by actual historical events. This is that type of game. So far, the story is pretty fantastical, but still fun. I have only played the single player campaign, and so far, I like it.
The graphics are sharp, controls are responsive, and the sound is good. I noticed a few times where the action paused for a second while the game was loading, but hopefully that will be minimized or eliminated by installing the game on the hard drive. This game feels highly polished, and I'm looking forward to finishing it and playing the multiplayer and co-op zombie modes.