The Fighter that was truly superior when it went into squadron service was the Me-262 Swallow. But it was too late to make a difference in the air war over Germany. Fortunately it wasn't introduced a year earlier!
In the present the F-15 is the most successful air superiority Fighter ever. But if you want an air to ground Fighter that could kick butt in air to air, the A-4 Skyhawk series was the best for the buck.
BTW, if anyone nominates the late model F-16's, I won't argue against it.
I've intentionally left out aircraft that have seen no air to air combat out of my choices
