Call of Duty is the Goliath of the video game world. The series has sold millions of copies and catapulted itself from a solid, World War II shooter to the sprawling multiplayer playground and Hollywood-style campaign that we know today. Call of Duty: Black Ops takes much of what made Modern Warfare 2 great and slightly expands and modifies it. That's not to say that there aren't mistakes to be found within Black Ops, but I think Call of Duty fans are going to be happy with Treyarch's latest effort.
The only thing I'll say about the storyline is that it's the best of the series.

You begin the game as Alex Mason, a soldier being interrogated for information that he can't remember. You play through Mason's memories in search for information. Sam Worthington, Ed Harris, and Gary Oldman deliver expert performances and really nail their respective characters. There are twists, some of which work better than others, and the plot seems to get bogged down and slightly disjointed towards the middle. But unlike Modern Warfare 2, Black Ops does a wonderful job of cleaning everything up for the finale.

People might be wondering with all the troubles at Infinity Ward, the original devs behind CoD, who is making this game? The answer is Treyarch, the team behind the moderately successful CoD 3 and CoD World at War. Both of which were WWII based storylines. But now this is their first venture into the Modern Warfare(sort of) world. The storyline is set in the 60s era of Cold War between the US and Soviet Russia.

The Single Player mode is the best FPS experience you're likely to have in the CoD series. Gritty, action driven set pieces, excellent voice acting, and larger than life action sequences, all these mash up to make a great game. Graphics are on par with Modern Warfare 2, but maybe that is because it is based on the same game engine.

The multiplayer is competent as well. That is to be expected from a game with the CoD name tag. Level up by earning kills, spend experience points on new skills and/or weapons. Become a respected veteran of the Cold War era.

I would rate this game higher than CoD Modern Warfare because of two reasons. The multiplayer is great, on par with that game. But the singleplayer is ust miles ahead in terms of duration and content.