Medical is not very tasty. I don't blame him for hating it..
Jemma was on Medi-cal allergy food, then wellness chicken before we got her. She hated both. She likes Iams ok, liked Eukanuba a little better, LOVED Purina ProPlan for sensitive stomachs (fishy) and REALLY REALLY LOVES the Solid Gold Wolf King (also quite fishy). I also just got Wellness Fish and Sweet potato for my dad's Jack (the most fishy food I smelled so far) and he was doing all sorts of tricks to get another kibble yesterday.
I think Fishy food is the way to go. Here are the ones I've mentioned in order of budget:
Proplan Sensitive stomach
Wellness Fish and Sweet Potato (MUCH MUCH better than proplan)
Solid Gold Wolf King (comparable to wellness but slightly more expensive).
Websites for the last two:
SOlid Gold Wolf King
Wellness Fish and Sweet Potato