I do not remember any other Televised "farewell speeches" in my lifetime. I think Nixon made a speech when he left, but under very VERY different circumstances. And I was only ten years old, and we didn't get many TV channels anyway.

Perhaps it is that President Bush still feels the need to explain himself and to try to control how his Presidency is pictured for posterity, while others realize that that is not something they can control?

I don't know.

Certainly no President has been perfect.