They explicitly all worship the same God so not "incompatible gods". I did not claim there were no disagreements about the nature of God, but that it only adds one to the GP's claim of 3,000 incompatible Gods. Even if Christians are completely right theologically, Jews and Muslims are still mostly right - one God, a loving creator, omnipotent and omniscient etc.
AFAIK most Hindus are pantheists, so believe on one God, albeit of a very different nature.
Buddhists do not necessarily believe in any god at all.
Buddhism and Hinduism are definitely compatible with each other. I know lots of Buddhists who make offerings in Hindu temples, for example.
Gods of many polytheistic religions are compatible, you just add more gods or identify similar gods with each other (e.g. Sulis Minerva who was also Venus). They can also be compatible with pantheism - you just add more aspects of God.
At the most almost all human religions fit into a handful of broadly similar systems.