I have a Denon dvd-5000; it won'd read cd-r's

If it was made close to or before the advent of CD-Rs, of course it won't read CD-Rs. Some CDPs made now won't read CD-Rs.

Beavis, when was the first year cdr recorders were available for consumers to buy?

If I just wanted arrognat answers, I wouldn't have posted on audigon. There must be something different about a burned disk, but if you think about it, all disks are copies; so there may be a chracteristic about fatory burned ones that can be reproduced. It's unfortunate that the tone of three of the answers weren't in any way trying to be helpful, but ignorant; at least I was willing to ask the question.

Best I can find the first consumer sold cd recorder was a sony, about 1990-1991. I believe your Denon dvd 5000 was sold in 1999. Is that about right. I have a old Sony DVP S500D I bought in 1999. It plays cdrs just fine. Still works great my grand kids use it to watch Disney movies. Why some do and some don`t, sorry I can`t answer that. But if yours don`t I don`t think there is any thing you can do.
Beavis is right on one issue. Even today there is some DVD players sold that will not play cdrs. Even some Sony models.