COD1 was the first 'real' game I bought for my personal computer. And it was totally awesome, the best WW2 shooter I had ever seen at the time. Great SP campaign and MP.
COD - UO, which was even better, with all the vehicles and other additions. Again, great campaign and MP, which I enjoyed for a very long time. (until COD4)
COD2, I played a part of the SP campaign at a friends house, and looked amazing again. I haven't had the opportunity to buy it myself. I can't judge the MP.
COD3, console exclusive. I've gathered it's rubbish.
COD4, change of the series towards Modern Warfare. Epic SP, loaded with drama. A true fresh start for the series. Superb MP, with addition of the perks. I'm still playing it to this day. It deserves all its 'game of the year' awards.
COD WAW, I borrowed it from a friend, and was quite sceptic because Treyarch had developed it. And still, the SP campaign was again epic. And the high amount of gore was also a nice touch. I enjoyed every bit of it. The MP on the other hand was utter crap. I hated it to the bone.
COD MW2, again a breathtaking SP campaign, some say a rather short one. Also liked it alot. MP, no fun at all. It's there for when you're bored and don't care if you're utterly massacred.
Now, COD: Black Ops. I've been waiting since UO (2004) for Infinity Ward to develop a game set in the Vietnam War. (At the time I was playing the game 'Vietcong', so.. yeah)
If I buy it, I think it will be for the SP campaign. Also, I'm crossing my fingers in he hopes that the main focus will be on the look and feel of jungle warfare, and not of 'Rambo-like' one-man-army over-the-top epicness. But chances are small, I guess, since this looks like a trademark of COD nowadays. Also, I do not care (yet) for the other missions, we'll see.
That's what I have to say about the matter ^^
