The graphics and also some games are designed in such a way that you wont be able to read the texts at all if your TV isnt HD. I cant remember where I encountered this problem, but it was in one of my old games back in 2006. Back then I didnt have a Hdtv.

Basically they made some texts in the menus, load screen or whatever so small that when you're missing the extra hd pixels those texts are reduced to nothing but meaningless boxes.