Depends on what you define as perfect? Immortal, Omniscient, Omnipotent, Benevolent, etc?
If you just mean humans being decent creatures without doing evil, well I think life would be a lot more boring than you'd expect.
We wouldn't really be individuals with choice either. The whole point of free will is that we can choose to take a path; but if we are limited to a certain way of thinking, then we wouldn't be ourselves.
Without evil there can be no good, and without good there can be no evil. We define these things in contrast. With evil, we can see the value of good. But without evil, we would just take these things for granted.
When a man dies and reflects on his past, he can see whether he was good or evil. But in a world without evil, a man can't be content with the idea that he was above temptation in the end.