Cebird, thank you for not bashing my answer and giving your opinion. For Israel, I don't think you can argue for or against them unless you have someone to argue against. For instance, between Israel and the US, I'd rather have the US. Between Israel and Canada, I'd much prefer Israel.
Modern Israel is not a Civilization. The people of the Jews have done some amazing things such as surviving Holocaust. The hand of God was upon them for sure. However, this does not mean that they were truly a civilization. They lived in Germany, France, and other countries.
Ancient Israel drove out the Canaanites, secured their nation against innumerable odds, held it for hundreds of years against all odds, and only fell because, due to their falling away, God withdrew his protection.
Of course, one argument AGAINST their inclusion is that their very existence happened because of God, and miriculous victories giving them their land. That being said, Joshua was a great military leader, the Judges were great leaders, David and Solomon were great leaders.
If they included Modern Israel, it wouldn't bother me outright, but whoever they left out to include them would dissappoint me most likely. I don't think Modern Israel is truly "A civilization," to grace the top 18.
Ancient Israel? Not too sure. Depends on who gets cut to include them. I think they would be a pretty good addition. Personally, I'd like to see King David their leader, a warlike leader I'd believe to be more interesting than a wealthy Solomon. And he was a better king.