The "best" CD-R media depends on your drive, on what speed you burn at, and it may also depend on what characteristics you consider important, such as toughness, the ability to be burned at maximum speed, or how easy it is to read/play in different drives.
That being said, the two best CD-R media in my opinion are:
- Verbatim DataLifePlus Crystal + Super AZO CD-R 52x
- Taiyo Yuden CD-R 48x (mine are under the Plextor brand)
Some drives will burn one with better quality than the other, but most drives will burn these two media very well.
Another important issue is burning speed. Only the best drives will be able to burn CD-R media at maximum speed with the same quality (readability) as when burning at a slower speed.
Many would tell you to burn Data CDs at 32x and Audio CDs at 16x, and although that is very simplified, it's a good rule of thumb.
So I suggest you first try to burn your current CD-R media at 16x when you're burning Audio CDs or MP3 CDs for your players, and you can increase the burning speed to 32x for Data CDs.
If that doesn't work for you, try getting some better CD-R media like either of the media I listed above.