do regular DVDs look okay on an HDTV? I'd like to get an HDTV but I'm not going to restart my movie collection on Blu-Ray.
Hmm...good question, it all depends on what type of HDTV it is, it's screen size, and of course; what type of scaler it has.
Typically good HDTV's will have a good scaler, most notably if you are a movie fanatic most Plasma's do a better job since it has deeper blacks and has slightly better color saturation controls.
For gaming however, LCD's are just as well, sure the colors aren't as great as say some of the best plasmas, but they don't have any glaring and most importantly don't leave any screen burn which Plasmas are very susceptible to if an image if left in place for a long time, of course, higher end models and newer models have gotten more resistant and have better controls against it.
I own a 720p 43" Samsung Plasma and typically speaking, most DVD's and 6 generation consoles (I.E. PS2, Gamecube) won't look so good even with the HDTV's built in scaler since their signals are analog and are mostly in 480i, however there are some games for those system that do support 480p progressive mode which improves the picture quality on HDTV's, of course component cables are needed as well as the game supporting such a mode.
I use an external scaler and the results are outstanding, though I wouldn't suggest it unless it's a large screen over 40".
For most current generation systems, gaming will not look bad since they are obviously made for HDTV's, excluding the Wii, and it depends what kind of resolution you get as well, if it's of a higher resolution, say 1080p and a PS3 game only support up to 720p, then you are bound to get jagged edged, even though it's in HD, it won't be "True HD" since the game wouldn't support, otherwise if you don't care for graphics to much, then 720p or 1080i aren't really gonna make a difference on current gen gaming. Blu-Rays however look amazing and should be experienced on an HDTV.
Well, for those of you concerned about lag, well some HDTV's actually have a "Game Mode" which will typically reduce lag ranging from 6ms-18ms, but this mostly applies to older systems such as the PS2 since an HDTV has to upscale and de-interlace an image with it's own resolution, theryby the time to process it it will result in lag, unless an external upscaler or Game Mode is used which would reduce it significantly, but at the price of typical inferior picture.
tl;dr: If you want to watch a bunch of DVD's on a large screen without a scaler, it will look like crap, but if you own a PS3 or 360 then you should be fine since it actually upscales them with it's internal scaler, be warned, it won't look as good, and isn't "True HD" compared to Blu-Rays, as for gaming, if you guys play most of the current gens then you should be fine, especially if you don't plan on viewing on a large set, even the Wii looks okay with component set to 480p.