How do non-Catholics understand Catholics' fulfillment of the Great Commission?

One argument in favor of Catholicism that I see as particularly convincing is that Catholics have done the best job of fulfilling the great commission. This is born out in the fact that Catholics have over a billion members worldwide, larger than any other Christian group. Matthew 28:19-20: >Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, 20 and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.” (NIV) Since Catholic's have done the best job fulfilling Christ's command, doesn't this mean they are closest to Christ's teaching and thusly the true Church?