So, overall, I think that the claim that the attestation to the life of Jesus is "the best attested event of history" is definitely wrong, and the claim that it is "the best attested event of ancient history" is also an overstatement -- but not by much. Certainly, given the circumstances of the time, the amount of information available about Jesus from the contemporaneous biographies is (to my knowledge) unprecedented.
I'd go a tad further. The article mentions that Jesus' earthly background does not mean that someone like him would have much written about him because at the time they didn't know how important Jesus is. Of course more would be written of Julius Caesar. I think that the very fact that we as everyday people know so much about Jesus and next to nothing about the other itinerant preachers, and would-be messiahs shows us that Jesus is different. That Jesus wasn't and isn't like everyone else who has walked this planet. Regardless of whether or not you believe the things Jesus said and did, the fact that you can know something about Jesus is indisputable. The truth is Jesus' life affects yours on way more levels than Julius Caesar's did. Jesus matters.
CADRE Comments: The Best Attested Event in History?