Vanderbilt, Kentucky and Miss St. = Awful
Ole Miss, South Carolina, Arkansas = They occassionally have good teams occassionally don't
Auburn = tends to be hit or miss as well. had some very strong teams in the middle of the last decade
Alabama & Florida = even those schools struggled at the start of the decade; obviously they are two of the most dominant schools in college football right now though it will be interesting to see how Florida progresses under Brantley going forward; most likely last week was a serious anamoly.
Georgia and LSU have been pretty good
So yes the SEC has been very strong the last four years winning the BCS Championship. But at the start of the decade the conference was nowhere near as strong as it is now and teams were still playing weak OOC schedules.
I spent a little time looking at wins and loses for the SEC & the PAC-10 for the last 5 years. (since scheduling is easily done inside that range and I don't have the time to track wins & losses for that many teams for 10 years)
The three teams you said sucked, Vandy, Kentucky, and Miss State have 5 year winning percentages of 38%, 52% and 38% repectively. Although, Ole Miss has a 5 year winning percentage of 46%, so lets use them as part of the bottom 3.
The three bottom teams in the PAC-10, Stanford, Washington St, and Washington have 5 year winning percentages of 39%, 30% and 27% respectively.
Bottom 3 in the SEC have 5 year win rates of 46%, 38%, and 38%.
Bottom 3 in the PAC-10 have 5 year win rates of 39%, 30% and 27%.
So the bottom 3 teams in the SEC have better 5 year records than the bottom 3 in the PAC-10.
South Carolina, Arkansas, and Auburn have 5 year winning percentages of 56%, 56%, and 67% respectively.
Six of the 10 teams in the PAC-10 cannot boast a 5 year win rate of 56% or better.
Which leaves us FL, LSU, AL, and GA. Their 5 year winning percentages are 85%, 77%, 74%, and 74% respectively.
The PAC-10 has only one team with a 5 year winning percentage of 74% or above, and that is USC.
Add in the fact that LSU, FL, and AL have won BCS Championships, and Auburn was snubbed for one, while the PAC-10 has only USC to offer up as a BCS Championship winner.