It really depends on how you define "best". If best means "win the national championship," which seems fairly obvious, then yes, the SEC is the best conference in the nation, as they have won 7 MNCs in a row.
So they've produced the best team seven years in a row, but that doesn't necessarily make it the best conference. The best conference is the conference that continually outperforms other conferences in head to head match ups (ie more wins vs conferences). Conference A's #5 team should be able to consistently beat Conference B's #5 team. Here's a look at conference vs conference records:
||||||||| SEC ||| ACC ||| BXII ||| B1G ||| PAC ||| Winning Records
SEC ||| - ||| 280-135 ||| 75-63 ||| 77-53 ||| 67-39 ||| 4
ACC ||| 135-280 ||| - ||| 39-49 ||| 50-65 ||| 20-30 ||| 0
BXII ||| 63-75 ||| 49-39 ||| - ||| 170-229 ||| 135-121 ||| 2
B1G ||| 53-77 ||| 65-50 ||| 229-170 ||| - ||| 234-242 ||| 2
PAC ||| 39-67 ||| 30-20 ||| 121-135 ||| 242-234 ||| - ||| 2
So even by that definition, the SEC is the best conference. The B1G, PAC 12, and Big XII are all interchangeable, and the ACC is the bottom of this list.
But this is data from a huge time frame--perhaps a better definition of the best conference would be a look at these records over the past 7 years, the same amount of time the SEC title game dominance started.
