I actually wasn't talking about Jesus, though you are technically wrong in your statement; Messianic Jews (and they ARE Jews) do believe Jesus is God. Rather, I was referring to YHWH whom all Christians and Jews can agree about!!
Well, not really. Most religious Jews do not consider Messianic Jews as Jews, but as Christians.
The reason for this is that the Trinity which many Christian denominations believe in (Jehovah's witnesses don't as far as I know) is seen as idolatry and thus not compatible. Since Messianic Jews believe in the Trinity, this is the case.
Believing in YWVH and Jesus as Gods is ultimately seen as polytheism for Jews and many Muslims feel the same way.
As in traditional Jewish objections to Christian theology, opponents of Messianic Judaism hold that Christian proof texts, such as prophecies in the Hebrew Bible purported to refer the Messiah's suffering and death, have been taken out of context and misinterpreted.[137] Jewish theology rejects the idea that the Messiah, or any human being, is a divinity. Belief in the Trinity is considered idolatrous by most rabbinic authorities,[138] though there is a minority view that it constitutes shituf (literally, "partnership"), an association of other individuals with the God of Israel. While shituf is, according to some opinions, permitted for gentiles, it is considered idolatrous for Jews.[22][139] Further, Judaism does not view the role of the Messiah to be the salvation of the world from its sins, an integral teaching of Christianity.[104][140]
In this regards Muslims and Jews are much closer than Jews and Christians.