Depending what it on it, it may or may not be sufficient. If it shows that Barack Hussein Obama, born in wherever-it-was Kenya, is his legal father, then it would also need to be legally documented that BHO Sr was not a US citizen. Entry and exit records would need to be found.
If the long form shows he was born in Hawaii, but also shows that the filing was a late one, or was as an unattended home birth, then the Kenya BC becomes more important. It would need to be refuted, because those sorts of filings are markers of possible fraud, since they are pretty unilateral, with no doctors signature, no hospitl registrars signature, etc.