These are so common in zombie lore now, it's like saying WoW copied Everquest by making elves good with magic.
with that line you hit the nail with the hammer
l4d gets the credit of what killing floor started thats why people hate the comparisons.
its same as with mmo's on mmorpg.com wow is nowhere to be found in the top 10
the reason for this is because the older mmo crowd knows that wow is way more easy and casual, and that wow has some ignorant people that call EQ **** cause it looks bad, while they havent even played it. thats what generates hate toward commerical titles. and most of the underground crowd refuses to play them.
now thats the same what i feel with l4d and KF
l4d is well known. KF a bit less, and if people compare l4d to KF most of the old players will see it as a kind of insult, and jump into defence imidiatly.
i personaly like KF more but i will not start gettin flamey if people talk about l4d.
i understand some of this anger. if titles really get screwed up, like Rainbow six vegas did for the R6 series, or what oblivion did to the elder scrolls fans, but both kf and l4d are not sequels of any series, and are seperate games