As an experienced shotgun user, (5/6 Shotguns Golden), I can confirm that the two greatest shotguns in the game are the Barret .50 Cal and the Type 95.
The .50 Cal has an unlimited range, unlimited rate of fire, and a very common one hit kill radius. The Type 95 has high damage, 3 round burst, and high fire rate.
All of the "shotguns" have slow fire rate, a very low range, and they aren't very powerful unless you have damage or range.
"If FIFA can't teach you how to kick a ball, and Guitar Hero can't teach you to play guitar, then how does Call of Duty teach you how to use a gun?"