2.35 to 1
most, if not all, of the widescreen DVD's will leave bars on the top and bottom, even of a widescreen format HDTV like a Mitsubishi 55 inch silver series.
You may be able to switch to a "zoom" format, which will make the bars go away, but it will clip some of the picture off both sides as well.
the widescreen TV is a 16:9 format (roughly 1.8 times as wide as high) while the widescreen DVD will show in 2.35 to 1, as was used originally in the theater. it would look even worse on a normal 4:3 (1.33 to 1) ratio. You could buy "fullscreen" DVD's to get rid of the bars, but they have just been pre-zoomed for you, and the sides will still be clipped.
check the DVD box to see what ratio it provides. Some (like the original release of Resident Evil 1) will use an entire 16:9 widescreen format TV, but most are 2.35 to 1..
unfortunately widescreen TV's are a best fit from a normal TV and a theater. they are trying to meet in the middle of the two, but don't do a really great job of either, for now. as more HDTV programming becomes available, the old TV format will die off. someday in the not to far future, normal people may be able to buy 2.35 to 1 TV's....