You know, there are millions of people who think the UN is biased in FAVOR of Israel (despite the fact that Israel has attacked UN personnel on at least two occasions that I can recall in the last few years). I would think the truth lies somewhere in between. Some members of the UN favor Israel and some oppose it. The UN is a democratic organization, to a point, but a few countries can exert more influence than others.
Membership in the UN is voluntary, and Israel joined 60 years ago. It has had a major chance to shape the UN from almost the beginning, and is one of the more senior member countries. Palestine is not a member state of the UN. Who would logically have more pull with the organization?