While I'm not sure how McGrath answered the question, I can give an answer to the latter half of your question: What makes Jesus unique among other major religious figures of history?
First, to my knowledge, Jesus never claimed to be a prophet or messenger from God; whereas, every other major religious figure claimed to a prophet or messenger from god. Jesus, however, claimed to be God himself (John 14.9). Moreover, we also see him claiming divinity in his seven "I am" statements in the Gospel of John. In the original Greek manuscripts, we can literally translate it this way: "I, I AM...". So, in most instances when he made an "I am" statement, the people wanted to get physical with him not because he said "I'm the bread of life...", but because he literally said: "I, I AM, the bread of life" (John 6.35-42).
Secondly, while Jesus was crucified and buried, he did not remain dead. The Bible claims that Jesus was resurrected from the dead after the third day (Luke 24). Now, if one were to counter this point by saying: "Well, his body was stolen by the religious leaders who wanted him dead", I would simply ask: "Then why didn't they produce the body to put the supposed 'rumors' to rest when the disciples began claiming he was resurrected?". Every other religious figure in the world has remained dead; Jesus did not.
Thirdly, we know that Jesus does in fact change lives--even today. People are still being converted to Christianity almost two thousand years after his death, burial, and resurrection. Moreover, people are willing to die for the cause of Christ (look at the Apostles in the New Testament and the early Christians). People do not die for what they know to be a lie. Now, before one counters with: It could just be a mass delusion, I would point you to the book of Acts and read the account of Pentecost. It is unlikely that thousands of people could have participated in a mass delusion together and all had the same outcome.
