Belief in Christ or Prophet Mohammed, as the case may be is the only way way to go to heaven. According to both these religions, the unbelivers went to hell. as these two religions did not believe in another birth after the present one, the entire emphasis in their teachings was on going to heaven after death.
Hinduism on the other hand,postulates a series of births, and proclaims that the sorrows and sufferings of each life, like its joys are the result of our karmas (deeds) in our past lives. Consequently the Hindus do not speak of eternal damnation, as the Christians and Muslims do. The buddha too believed in karmas and cycle of births because he was the product of the vedic tradition.
The logical consequence of the assertion that only those who believed in Christ or in prophet Mohammed, as the case may be, will go to heaven, is that those who were born in the world before the advent of Christ or prophet did not attain salvation. This position cannot be accepted. Moreover, these two religions did not give a rational explanation for present sufferings or provide a remedy for them.
The Hindu theory of karma and cycle of births and deaths alone offered a satisfactory explanation. Each person has “earned” the sorrows of his present life, and can “earn” happiness in his present and future lives, by the performance of good karmas.