If you want to add variety to the diet, fresh cooked, oily fish or fresh meat is the way I recommend you add the appitizer value. Tinned oily fish in oil is good too.
There are so many vaiations & quality of raw materials in commercial wet & canned food to really make sense. - If you buy it fresh (or frozen) & prepare it yourself, you really know a bit more what you are giving.
The factory stuff must pass some quality standards & may be nutritious, but never forget the cause of the BSE problems. - Bad materials, not properly sterilized in production of feed.
I once went for an interview at Pedigree Petfoods factory for a job - after that experience , seeing the stinking, rubbish that they cooked up, I would not use their products! I'm far from squeamish but that really made me gyp!
Ian