Is is true that radial engine interceptors (Focke-Wulf 190, Zero, Frank) IN GENERAL did not perform as well at high altitude interceptor roles against our B-17's, B-24's and B-29's as did the in-line liquid cooled engine interceptors such as the ME 109, Focke-Wulf 190D (langnase), and Ki-61 Tony?

If so what was it about the radial engine that made it perform less well at high altitude?

in reality the Fw 190A's did well against B-24/B-17's at all altitudes, it was a better gun platform than the Bf 109, what the Fw failed to do was to take on Allied escort fighters at 28,000 feet plus, the 109 was better in that role if we consider any LW fighter well enabled to take on US fighters which there was not.......... the Dora was to few to really prove itself, and it was not regarded as a bomber killer due to the lessened cannon arms

..put simply aspirated engines such as radials require an air supply - of which there is less available at altitude..check this link

Golden Age of Aviation Aircraft Engine Development.

Thank you FalkeEins.

I believe that this statement is misleading. Normally aspirated engines can be radial, straight, or vee. And the same is true of boosted engines. F8F's and B-29's all had supercharged radial engines. I am not sure whether the Axis had turbo- or superchargers on their radial engines, but there is nothing about a radial engine that intrinsically rules out the addition of a booster