I believe mankind hit its peak on July 20, 1969, the day that Neil Armstrong walked on the moon. It was a "first" to beat all other firsts. Sure after that we went back to the moon a few more times, and we have done other interesting things since then, but I believe nothing will ever top this day.
Today, we do not have the ability to return to the moon. The truth is, we do not even have the ability to put men into low earth orbit any more. Even though technology has advanced in many areas since 1969, I doubt we will ever be able to put men on the moon again. It costs lots of money, takes lots of hard work, and requires lots of people to agree on something.