When I say there are similarities, I don't mean that Buddha and Christ grew up together and studied the same belief structure before shaking hands and going their seperate ways...not that you said anything to this nature...
Yes, these are significant differences, but they relate to the afterlife. Just because two people have different ideas about Hevean, doesn't mean that they can't work for the same thing on earth while they are here.
Preaching for peace and the renouncement of material needs are not trivial coincidences, nor are the intentional seperations from society(Jesus, obviously, went to the desert; Buddha to the forest), and the three trials each underwent before finding their ultimate enlightenment-- especially when you consdier the vast differences between Buddhism and Christianity.
The similarities are in the spirit of the preaching, not the technical, point by point instructions each gave, considering Buddha and Jesus had very different views concerning, well, quite a bit.