HAHAHA!
First, I'll clear up the best selling shooter thing
Duck Hunt (28 million sales) has sold more than CoD4 likely ever will
Second, I don't think it's anywhere near the best shooter ever. I prefer BF1942, CS1.6, Goldeneye, Perfect Dark, Time Splitters 2, Red Steel 2 and a whole host of other games (basically anything that actually has a health bar for example)