My understanding is they appeared at different times to different people. They are like Physicians and diagnose the remedy for the illness of that time. The remedy for one time and sickness will be different for a different time and illness. So They prescribed what was the best medicine for that time and the different people they appeared amongst.
That makes sense, though I disagree. I honestly feel we try to put all the world prophets in line with each other to kind of smooth out the differences and make peace.
Someone told me once when I said I still am Catholic regardless if I practice (taking sacraments is a marriage to the Church) and they said "you're trying to keep one foot on either line 'just in case'." However severely wrong this person was, he does have a point. We can't keep trying to make peace by finding a medium between two sides.
If one side of the world speaks Chinese and the other side speaks French, and a prophet from both sides had goals to to save the world that doesn't mean their worldview, culture, and language are similar or the same to each other (just in different parts of the world and/or time periods). It means they are totally different from each other.
So, Jesus Christ is completely different than The Buddha.
They were in different times, which means different generation (like in the 80s who would have thought we'd have a Star Trek blue tooth phone in our ears?) Same then. The Buddha came years before The Church and Bible were even thought of and put together. His goals were different in method. He wanted the
people to reach enlightenment.
So, I don't see how they can go together, really. Jesus looked out to his father for his divinity. The Buddha looked within himself for enlightenment. The Buddha denied that divinity (god/s for example) was a part of our enlightenment. Jesus said divinity/god was a highest requirement.
The time difference doesn't make a difference. If they were siting side by side today and had a good conversation, Siddhartha Gautama would have a fit knowing that Jesus' approved of Jewish teachings of animal sacrifice-way back in the day. Then he'd be mad that Jesus' disciples even promoted that Jesus himself sacrificed himself physically when the way to help people from sin/suffering is to be with them physically not just by faith.
Since Siddhartha is The Buddha, I don't think he'd fret anymore. However, Jesus did yell and he did get upset at his own people and even at Satan. So, I honestly don't see a strong comparison other than they both are human and want to help the world. (Don't most of us, though?)