Not read al lthe replies so sorry if I'm saying things that others have already said.
The 3 cats that live with my Mum only eat Hills dry food and will not touch wet food at all and have never had any health problems from this (2 girls and a boy) but Team Svartalfheim's happily eat a mix of dry, wet and raw.
If you want to feed only dry then make sure it is a quality brand such as Hills, Royal Canin, James Wellbeloved, Purina Pro Plan etc. Will he eat chicken or anything like that? If he will then it might be worth trying Applaws or Almo Nature food (they are complementary so feed alongside a complete dry food such as one of the ones above) Nature's Menu wet is also good. It could simply be he doesn't like Whiskas as there's basically no meat in it so a high meat wet food might convicne him that wet is good sometimes.