Most videos you will find have been ripped & converted so they can be burnt directly to cd but can also be burnt to dvd. So their resolution sizes will probably vary 352 x 240 to 480 x 480 pixels. If you want some hints on downlding videos see: Movie download issues

As for direct rips, you're looking at between 4-8.5 GB files. Not so many people are willing to share files of that size.