DVD-R Iincopatability?

Maybe some one can help me out with this. I have an LG unit that I can record on and we tried watching the DVD-Rs on a friends Sanyo and also RCA units but, they don't load and play. We even tried our computers using Windows 7 and Windows 8 and the same thing the disc is not recognized.
What I have recorded is very valuable to me is there some way I at least can them transferred (if necessary) so that we can watch them on anything or what seems to be the problem? I could really use your help. Thanks
This from Wiki
This new format, among other things, resulted in DVD-R being unofficially referred to, in error, as DVD "minus" R. However, DVD "minus" R is not correct, according to DVD-R consortium recommendations; it is, in fact, a dash (i.e. DVD "dash" R). DVD-R and DVD+R technologies are not directly compatible, which created a format war in the DVD technology industry.

To reconcile the two competing formats, manufacturers created hybrid drives that could read both — most hybrid drives that handle both formats are labeled DVD±R and Super Multi (which includes DVD-RAM support) and are very popular.

I am not up enough on DVD to know if this could be a factor but something to look into.
It's possible to have DVD-R and DVD+R compatibility issues, but its very rare. If you set out to find a non compatible drive on purpose, it would be a difficult task.
I did finalize the discs, they are DVD-R. I also tried titling them with still no success, file explorer in Windows does not show or list them, they just won't read at all. Albert looks like you may have found the answer for me, as I feared that it may be a format difference and the only way around that would be to have them rerecorded (if that's even possible). Thank you all for the help and I can still give the data recovery program a shot too that might work so that I can get 'em to play on the TV.
Windows is not good for this type of thing. Download and burn a live Linux distro to a DVD. Live means you run the OS directly from your CD/DVD rom drive in your PC. It doesn't alter your computer in any way. When you are done, you remove the disc and reboot the computer, and everything goes back to the way it was. If you go to distrowatch.com, you can find hundreds of live distro choices. Pick one from the list of the top 100 you get to when you scroll down the home page a bit.

Unless you have a very old, first generation DVD drive, the chance of you having a problem with dvd- blanks is highly unlikely. They usually list the formats a drive is compatible with right on the face of the drive itself. If not just do a search for the model you have, and check the specs that way.
Rsjm80, we still need to know whether the discs are playable on the LG unit they were recorded on. If they are then it should certainly be possible to transfer the video to another device even if you have to connect the LG unit to another recorder. I have a DVD recorder that, in addition to the SP/LP/XP length options, includes a flexible (I think it's designated FR) mode that basically matches the compression to the length of the program being recorded. This uses the entire DVD while ensuring the best quality possible. The instruction warn that using this mode may make the DVD unplayable on other equipment.
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