Ummm, are you serious? Almost everything. I am sure there are Lego fan websites that have lots of images.

Wheels used to have a metal pin that stuck out, and went into a 2x4 axle block.
There were 3 sizes of toothed gears. The largest was about 3" diameter. (and they went on the wheels)
There weren't any of the flat pieces (1/3rd height).
All the pieces that are now used as control panels and such used to be roof pieces.
And they had large, full height building plates.

And lots more. Things I recognize instantly, but are hard to describe in words.