I believe VCDs are mpeg1 format, whereas DVDs are mpeg2 -- much better quality.
A CD can only hold about 20 minutes of video at DVD quality -- even if you have the hardware and software to make the transfer. You can't of course, make digital copies of DVDs without illegal software. You could make excellent copies with an S-Video card, but you would need a large stack of CDs to do a movie.
DVD burners are about $400 and blank DVDs cost as much as the movie you would copy. Plus there are format problems, and not all DVD players will play homemade disks.