Ok, here's the skinny.
TVs use a resolution of 720x480. It's an odd thing, too, since that isn't exactly 4:3 (640x480 would be). Many people will tell you that 720x480 is wrong, but they just don't know. Yes, that's the resolution of a standard DVD. No, it isn't a mistake stemming from that. If you want to see the difference, get some real capture gear for your PC. Capture something at 720x480 and watch it on your TV at the same time. The edges (40 pixels on each side) aren't shown on the TV. On the PC you would see a little more of the scene of whatever you are watching. In the good old days, we just called this NTSC. 720x480 @ 60 interlacing fields per second, generating ~29.97fps. In modern HDTV times, this is called 480i. Resolutions for TV are stated as their vertical resolution* followed by an "i" for interlaced or "p" for progressive. Progressive is considered better than interlaced (full images instead of interlacing fields), though some research suggests interlaced is better for action. Personally, I think anything interlaced looks like complete crap, especially during action.
*There are two methods of stating resolution. Vertical in this case means the number of horizontal lines there are in a vertical cross-section. Essentially, how many left-to-right lines there are from the top of the image to the bottom. The other use of "vertical resolution" is essentially the opposite--how many vertical lines there are.
Anyhow, not important.
In order from worst to best, consider the following resoultions:
480i - TV, some DVDs
480p - Some DVDs
720i - Early HDTVs and cheap units these days
720p - Early HDTVs, mainstream
1080i - Mainstream
1080p - Good sets (1920x1080)
DVDs when played on your computer are already upsampled if you run a resolution higher than 720x480 (and you do). There isn't really anything you can do to make them look better. You're watching a much higher resolution display much closer than you would a TV. The compression artifacts are going to show up a lot more. There's nothing you can really do about it to make it look like you were watching it off a TV. The DVD drive itself has absolutely nothing to do with it. It only reads (and most likely writes) data. It doesn't have any hand in playing the movie itself.
If you are looking for a good DVD+/-RW, I'd suggest the NEC ND-3550A. No matter what unit you get, it isn't going to look different on your PC. You might look into using software with realtime noise reduction, but that's only a bandaid a problem stemming from the DVD format itself--using medium bandwidth MPEG-2 compression. It's a sucky compression and they've only got so much space on a disc for 1.5+ hours of video. DVDs just look bad. TVs are more forgiving because they're lower resolution and (more importantly) you sit much further away when watching.
It's got nothing to do with what hardware plays your movie. It's the DVD itself that sucks. They all do.
