Carrier air groups should be judged against their mission

What was the best carrier air-group composition for each navy during the Second World War?

It depended on the mission; Ark Royal's Skua-and-Swordfish group made sense for strike operations but left weak air defence.

There is no single best wartime carrier air group without first defining the carrier's task. Ark Royal's early-war mix of Blackburn Skuas and Fairey Swordfish is a useful example: it could be well balanced for delivering strikes, yet poor at fleet air defence. A composition optimized for offensive sorties may therefore look deficient when judged by combat air patrol or interception requirements. The useful comparison is between aircraft, deck capacity, and assigned mission at a particular date, not a universal fighter-to-bomber ratio.