If Jesus lived a perfect life, then so have thousands of others
One of the central teachings of Christianity is that Jesus Christ lived a perfect/sinless life as a mortal man on Earth. Most Christian denominations additionally claim that Jesus is the only human of whom this can be said, although some attribute that quality to a few other individuals as well, such as Mary.
The gospels (Luke especially) actually paint a lively, colorful picture of Jesus. He lives with his disciples, as one of them. He helps people, and teaches them. He curses. He celebrates. He questions God. He gets angry, quite often. He heals the sick.
No one familiar with the gospels will deny that they describe Jesus as a man of great virtue, goodness, and supreme wisdom. To live life to the standards set forth by Jesus is a high ideal to aspire to, and to achieve it is a rare thing indeed.
But of course, it is not unheard of.
History is actually full of descriptions of people whose (claimed) virtues match those of the biblical Jesus. Socrates, Buddha, Marcus Aurelius are just some famous examples that come to mind, and many biographies of Christian saints similarly describe people who apparently lack any vices whatsoever, while dedicating their entire lives to the benefit of others. Of course, the actual number of individuals throughout history of whom this can be said must be in the thousands, with most of them having faded from memory.
Indeed, there are literally hundreds of thousands, if not millions, of people alive today whose entire existence revolves around service to others. They are healers, teachers, and protectors, all of course with their own uniquely human qualities and attributes – just like the biblical Jesus. There is no discernable quality that sets him apart from them.
Therefore, to claim that Jesus was truly the only human to live a perfect life seems to imply one of the following:
1. All historic accounts of other people living "perfect" lives are fake/embellished (but not the one about Jesus of course) and they in fact were not as blameless as their biographies say.
2. Jesus alone lived a perfect life by definition, that is, because he alone was the son of God rather than because of his actions (a variant of the "God is good because he is God" tautology).