Despite significant similarities between the lifestyles, morality, and some ritual and mystical aspects of Christianity and Buddhism, there are at least two decisive differences.
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.
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.