The clearly Messianic prophesies all state that the Messiah will bring world peace and restore the Jews to the land with the Messiah as King. THIS HAS NOT HAPPENED YET.

The standard Christian answer is that there will be a Second Coming. There are a number of very serious problems with this:
1) What is the source for this in the OT, none of the Messianic prophesies mention 2 comings. All of the Messianic prophecies have a first coming perspective. None of the verses indicate that the Messiah has been around before.
2) A second coming theory gives no credibility to the first coming. Using this theory, we could make practically anyone in history into the Messiah(i.e. Bar Kochva). Even if our random candidate accomplished nothing, we can claim that he will meet success in his second coming.
2) Jesus himself in the NT said he would return in the lifetimes of his disciples, he didn't. Here are some quotes:
Mark 9:1 "Truly I say to you, there are some of those who are standing here who will not taste death at all until they see the kingdom of God having come [that is, after it has come] with power."
Well those people are all long dead and Jesus hasn't returned yet.
Matthew 10:23
"But when they persecute you in this city, flee into the next: for truly I say to you, you shall not have gone through the cities of Israel, until the Son of Man comes"
From this verse we see that Matthew's Jesus promised to return before the apostles visited all the cities of Israel. It didn't happen.

The bottom line is, the Messiah will be the descendent of David who brings World Peace and Knowledge of God, as that has not happened the Messiah has not come.