I'm frustrated like you. My Denon 2900 won't play my bootleg DVD concerts (both +R & -R), but my parents $30 Koss from Sears plays them flawlessly. This isn't the first time I've heard about cheap players playing more than the expensive ones. I don't know why that is, but it really makes me mad!

M60s
VP150
QS8s
Marantz SR6003
Samsung LN52B550
Oppo DV-980H
Insignia NS-WBRDVD