I am only going to tell you about the Call of Duty games that I own
personally.
Call of Duty4: Modern Warfare
This was the fourth installmentt of the War series. Unlike
its predecessors, this game is set in the modern era,
instead of WW2, and is also the first to receive a Mature
rating. It was released November 7, 2007, and was released
for Microsoft Windows, Nintendo DS, Playstation 3 and XBOX 360.
As of May, 2009, Modern Warfare has sold over 13 million copies,
making it the most successful game in the series.
Call of Duty: World at War This game was
developed by
Treyarch
and it is the fifth installment of the main series, and returns to the World
War II setting of earlier titles. The game takes place mainly in the Pacific
theatre and the Eastern Front of World War II. The game was released on the
PS3, Nintendo Wii, XBOX 360, PC, and Nintendo DS. As of June 2009, it has
sold a little over 11 million copies. The favorite thing about this game
that I like the bonus Zombie missions. You can play either by yourself or
over the internet with up to 3 other people. The premise is that you are in
a secluded area, and you have to survive wave after way of Nazi Zombies.
With each wave, the number of zombies increases, the rate at which they come
at you increases, and the more damage you have to deal to them to kill them.
There are 4 different maps for Nazi Zombies, and sadly I don't think they
are going to make anymore maps.
Call of Duty: Modern Warfare 2
Modern Warfare 2
is the sixth installment of the series, and is a direct sequel to
Call of Duty 4: Modern Warfare, and continues the story from that
game. Upon its release, it sold 4.7 million copies in 24 hours, so I am
pretty sure it has outsold Modern Warfares 13 million copies