Despite significant similarities between the lifestyles, morality, and some ritual and mystical aspects of Christianity and Buddhism, there are at least two decisive differences.
For Christians:
1. The person of Jesus Christ is absolutely necessary.
Exactly the way in which Jesus is necessary, and exactly how this 'works' has various explanations among Christians; but for all Christians Jesus Christ is not merely an optional-extra (not merely a teacher or prophet or helper) - but an unique neccessity.
2. God the creator is a personage, and stands to us as a loving Father to his children.
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These differences have many and various implications, which differ among Christians; but these differences - shared among Christians of many denominations - constitute a core difference and distinction between Christianity and the Eastern religions.
Subtract them from a consideration of Christianity, and one does indeed have many shared aspects - but, once one has extracted them, the residue is no longer Christianity.