This was the only prophecy "given by Jesus" that wasn't too vague to matter, like the rest of his prophecies (see "wars and reports of wars"). But unfortunately, it was an epic failure. He didn't return within that generation as he promised.
As you see with EOMs post, prophecies mean whatever the hell you want them to mean. And salvaging this failed prophecy has proven quite the problem for Christians.
The Bible says what is says, and it doesn't say what it doesn't say. Too bad... most, if not all, of its adherents, don't believe this inconvenient truth.