VOBs from commercial DVDs are encrypted (Copy Protection or DRM). MC for Mac doesn't support encrypted video files of any type.
MC for Mac *does* play pretty much every non-encrypted format I've ever seen: AVI, FLV, MP4, MKV, and just about every CODEC I've ever thrown at it too.
VOBs tie you to a platform that can decrypt the contents. I would advise you to convert your VOB files to MKV or another unencrypted format. MakeMKV works with ISO files as well as real disks. It also works on Video_TS structures (the directory containing all of the VOBs, IFOs, etc.), so if you have the whole structure, MakeMKV can convert it, losslessly, to an MKV, which will have no encryption.
Once you have MKVs, MC and many many other players can read and play your videos.
Brian.