A couple of folks (most notably Slate's Jacob Weisberg) have been grumbling about "The Wire" getting dissed once more by the Emmys. People are suggesting racism played a role, seeing as how much of the cast was black. Maybe. But I think The Atlantic's Coates is more on the money in noting that "there were structural things. People loved the Sopranos because, in the end, it was about family. Plus the ensemble nature of the show made it hard to fix on one person."
"The Wire" was grand, sprawling, magnificent tv, but it was not the kind of show where you could latch on to a main character or characters. No one was especially sympathetic. And the closest the show came to having a flesh-and-blood central protagonist was McNulty, who was a complete asshole. I myself was in love with Stringer Bell--but they killed him off without a backward glance in Season 3. And Omar was fabulous, but he flitted in and out and was never fleshed out enough to work as a lead. This dearth of characters to relate to or even pull for likely goes a long way toward explaining why viewers never flocked to the show. (Well that, and it was so relentlessly grim.) But it may also go a long way toward explaining why Emmy voters never embraced it: "The Wire" was easy to appreciate but tough to love. And the series' artistry aside, many members of the National Academy of Television Arts & Sciences (who, after all, aren't exactly a bunch of high-brow critics) may prefer their shows more personally and emotionally engaging than David Simon was ever willing to allow his to be.