Mine wouldn't eat the food that they were feeding her before we got her (Eucanuba or whatever). It just sat there, and she would steal the cat's food. So I bought the same brand for her (which was much more healthy anyway, if you compare the ingredients). It's a brand I'm promoting now, so if you want to check it out, it's at
http://www.healthypetnet.com/kendalb
There isn't any corn or wheat or by-products, and I haven't done the math yet for dog food, but the cat food ended up being cheaper than the cat food I was buying before. My dog actually eats it... and sometimes I see the cats sneaking it as well. My dog still sneaks some cat food sometimes too, so they're even. ;-)