This is exactly what I have been saying about the book for a while (... and I doubt I am alone on this one). Without it the comics market in general would not be quite as vibrant as it is now. That's not to say there haven't been other strong influences like Marvel's assault on the Box Office... but a lot of the films are based on reboots of existing stories, unlike TWD which is by comparison fresh blood (even though it has had 10 years). So Marvel isn't exactly setting its modern market on fire.
WD changed TV, movies and comics for the better part of the last five-six years, and more importantly for the next decade. Period. I don't think that's hyperbole. Think of the scripts and shows which have been green-lighted, similar content that other networks are looking at now that they never did before (Sorry NBC...), the writers and producers who have come through TWD that are bringing that formula and experience to other networks, the cons, the fans, the haters, Skybound, etc.
It's an outlier. The idea of comparing it to another entertainment property as a gauge won't work.