I originally had that planned lol. I scrapped it because it seemed like it took too long. Let's do it anyways.
Call of Duty 4 AK47 MP5 -- handles silencer better than 74u; ammo sharing with M9 RPD M1014 Barrett
World at War M1A1 MP40 Browning -- DAT MOBILITY DB PTRS
Modern Warfare 2 TAR UMP RPD SPAS Barrett
Black Ops FAMAUG AK74u M60 SPAS L96
Modern Warfare 3 ACR MP7 ??? -- I have no decisive educated opinion on the LMGs, but I liked the LSW the most Striker Barrett
I have no opinion on BO2 besides the R870 being the best shotty. Most of the other weapons are fairly well-balanced on paper but my in-game experience has been all over the place and I haven't played more than a few games since they started patching stuff.