Some people have told me they found the Pyramids disappointing, but on both my visits I have come away highly impressed.
I think the problem is that, the media always stress the shear physical size of the pyramids, if you imagine them smaller than reality then they impress, but if you imagine them larger then you will be disappointed.
That said despite the crowds, It is incredible to visit something that people have travelled specifically to see for the last 4500 years!