I would investigate the media first. Try the DVD-RW movie burn on a set-top that is known to play DVD-RW. If you don't have access to one, you might be able to take the disc to a store and feed them some BS that you are looking to buy a DVD Player that will play your homebrew DVD-RW's and see if you can test it in a few display models. If it plays, then you know your burn is DVD-Video compliant so it burned "properly" even though it doesn't have menus, etc. This would narrow it down to the media issue at least. (PC software DVD players can play non-compliant streams ok).
PS2's aren't too picky about DVD movie playback. Mine will play DVD's that my Apex set-top rejects. As long as the data can be streamed at 1X and it's a DVD-Video compliant stream, it will usually play them. They may skip, stutter, pixellate like hell--but you'll get the DVD video routine text messages and it will try to play the movie. A game,however is different. It may need to stream data at 2x-4x in order to boot properly. I've run into this problem before while testing various DVD-RW's and confirmed that data rate is crucial in succesful game boots on my v5 US. Memorex are horrible for games, but usually do fine for movies--they stream an average of 1.1X when I test them in CDSpeed. My favorite TDK does fine for both and streams an average of just over 2x (2.08 typically). My pressed PS2's stream at about 3.2x typically.
If it ain't broke don't try to fix it! But, hell if you can tweak that bastard just a little bit more....hehehe.