in my opinion anything 48 percent or higher is fine.
In all honesty these charts can be very deceving.
Another thing about fizz is the following.
1-Despite what people say he does have a very high skill cap in all the tricks you can do with him, because of this it is quite easy to see who is a good fizz player and who is a bad fizz player. Thus making him a easy champion to fuck up on. IDC what people say, it's much easier to fuck up Fizz than it is to fuck up alistar
2-He has always been a counter or get countered champion. He is a master of punishing immobile mages, but he is also very vurnable of getting his butt pounded during lane phase from somebody who knows how to abuse proper range or match his mobility due to the fact he only has 2 ways to farm, Melle farm, or wait till it pushes to tower and execute a bunch of minions with trickster
So here we have a champion who is hard to master, and easy to counter pick against. Because of that his win loss ratio will never be exactly accurate.
In fact he is actually really good right now, becuase the champions who are strong in mid lane and top lane, are champions he can easily win against in lane.