I'd respectively disagree. MW is the peak of the CoD series and MW2 is what led it downhill.
Eh, MW2 had a great story and great gameplay, MW...Ehh. But I can respect your decision, it was the first Modern Warfare. I just believe that MW2 was the peak, and MW3 was the downfall.
The first Black Ops was also really good, it had a compelling story and a sharper gameplay, and the guns made it feel like you actually did some damage - even if it were the shittier guns.
If you want my absolute favorite, it would have to be World At War. Great storyline, a fun multiplayer, and the guts to show, well, guts. Not many CoD's actually show limbs flying off, unless it's zombies mode, which actually originated in World At War. So...