You mean video DVDs or data DVDs? If it is the former and there is no copy protection involved (commercial DVDs for example), then you can use Disk Utility for that.
If it is the former and you those DVDs are copy protected, use RipIt or FairMount or MacTheRipper to copy (rip) the video DVDs to your HDD and once you're done, you can rename the parent folder in which the VIDEO_TS and the AUDIO_TS folder reside to something like example.dvdmedia.
It is important that you add .dvdmedia (including the dot), which makes that folder a package, which opens the default software DVD player by double clicking on it.