There's nothing wrong with their widescreen releases. MGM have been using the same graphic on all their DVD's to display a comparison of widescreen and pan-scan. It looks something like:
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A lot of the time they have pictures of the movie in them. The problem is that while this may look correct for a lot of their movies, that were shot on anamorphic/wide stock, for those shot on an open frame it is not correct. The movies shot on open-frame often have more picture information in the pan&scan version than the widescreen version, like Terminator 3 (T2 also, actually).
Don't let that fool you though, movies like The Princess Bride that were shot on open-frame stock were always intended for a widescreen release. In fact, in those times directors would literally watch what they'd shot with cardboard coving the top and bottom of the TV screen to make it look wide-screen. In the open-frame release of The Princess Bride ("Pan&Scan") you can see boom mics that were not originally in the movie, because they were cropped out. The original theatrical ratio, short of a director-proffered ratio, is always the best presentation of the film.