I was looking at doing this too a while back. I have got the ripping/encoding process down to a science and get awesome results for all but the most "difficult" movies (dark ones like Harry Potter are tricky) which still show some pixelation.
Problem is that it is, for me, a 2 program, about 5 step process that runs for about 4 hours on my fairly fast (3.0GHz 1GB PC3200 RAM) PC. I end up with what looks like an original DVD quality .AVI of about 1.4GB in size for a 2 hour movie. Not bad, but not as simple as you are looking for. I tried a lot of "one button" solutions, but they never seem to get the settings right and I ended up redoing all of them with my other, multi-step process.
One nice solution that I have found to be successful for some people is to use DVD Shrink (freely available on the net) and make a duplicate of the original DVD, but reduced to about 4.7GB (designed to burn full movies on to single layer DVDs that are fully playable in a regular DVD player). This program seems to be more for people wanting to make a copy of movies from the rental store or borrowed ones from friends, but the reduced movie could be saved as an .ISO image and loaded with a simulated DVD drive, or saved as the DVD files into a folder (renamed to match the movie title so that it is easy to find) and then you could select that folder and open with your favorite Windows DVD application. With DVD Shrink, you deselect the options you don't want (I drop all but English for sound/subtitles for example, and sometimes kill off "extras" like director commentaries, etc). This means more space for the movie itself, and a better end picture. It is pretty much 1 button, but some "stuborn" DVD protections require a seperate rip from the DVD using something like DVD Decryptor.
Hope that this helps. Of course, this is for legal use only, if you use this information to make illegal copies of movies, it is your own fault, and I am not responsible for your actions!
