*Cough* mustang, SR-71 and F-22 *cough*
The A-10 is great and all (pretty much legendary) but there is no single best airplane. For example the Christmas bullet. It is considered one of the worst airplanes, but it was actually the best at a few things. Those things might be looking ugly, killing it’s own pilot, and being a bad idea, but it was darn good at it!