Christianity was founded by Hazrat Jesus Christ (May peace be upon him). Islam is founded by the last prophet of Islam Hazrat Muhammad (SAW).
Christianity and Islam are the ONLY religions having this understanding.
Allah (or God in English and same God worshiped in Christianity and Judaism); the Creator; is the founder of Islam. Refer to related question below.
Islam, Judaism and Christianity.
Jesus Christ is the founder of christianity.
One confused human being.
This is a tough question, because it is so non-specific. But to understand the answer to your question, you have to understand the relative positions of Islam and Christianity. Although Islam came 6-hundred years after Christianity, it is still Christianity that is the mainstream of human history.
Christianity, Islam
Islam, Christianity
The Bible is to Christianity as the Qur'an (Koran) is to Islam.
Judaism, Christianity, and Islam have all claimed the Holy Land for themselves.
Christianity, but Islam may overtake Christianity relatively soon.
Prophet: Jesus