AFC East: NE 3-3, NYJ 1-0, Buffalo 0-4, Miami 2-3
6-10
AFC North: Pitt 6-1, Balt 1-0, Cle 0-0, Cin 0-2
7-3
AFC South: Colts 2-2, Tenn 0-1, Jax & Hou 0-0
2-3
AFC West: Den 2-4, Raiders 3-2, SD 0-1, KC 1-1
6-8
NFC East: Dal 5-3, NYG 3-1, WDC 3-2, Phi 0-2
11-8
NFC North: Chi 1-1, Minn 0-4, GB 3-1, Det 0-0
4-6
NFC South: TB 1-0, NO 1-0, Atl 0-1, Car 0-1
2-2
NFC West: SF 5-0, Rams 1-2, AZ 0-1, Sea 0-1
6-4

Historically, they stand up well in direct competition with the best of other divisions. As for your "since 2005" criterion, if we want to examine recent success, well the conference champsions since then have been:
05 Seattle
06 Chicago
07 New York
08 Arizona
09 New Orleans
The West is the only division to send more than once team to the Super Bowl in that period. Five years too small? Double it then:
00 New York
01 St. Louis
02 Tampa Bay
03 Carolina
04 Philadelphia

Over a ten year span the West has had three conference champions, while the East has had 3, the South had 3 and the North only 1. Going back further we had St Louis and Atlanta in consecutive Super Bowls and then a couple more years and we are in the heart of the San Francisco era. The best of the West stacks up well against the best of the rest. And for all we know, the effort of banging heads with the 49ers when they could afford to keep a future Hall of Famer as a back-up QB or hold onto the best receiver in the game for as long as they wanted him, was what kept the second-class citizens of that division down.