Speed matters for subsonic aircraft. Above that it becomes a matter of conventional versus delta wings.

The conventional planes get more turn rate with more weight. F 18 has lower instantaneous than a eagle than a sukhoi. Excluding the planes with fuselage lift (f16) or thrust vectoring, this rule holds. If something adds weight, like thrust vectoring, this is a double benefit. The su 35 turns 90 degrees in two seconds in air shows. Likely the most maneuverable non experimental jet fighter ever created.

The f 15 has a clipped delta wing. With increasing size there's a tendency to put more weight in the back or move the wings back. Although center of gravity is not published you can use RC models to understand it, and they confirm the f 15 is more unstable than a hornet and has a cog farther aft of the wing edge. The hornet LERX compensated for its smaller engine and does not help lift versus the eagle. The sustained turn rate of the eagle is worse as it's a big plane and a partial delta wing. The f 15 has a black box and is mechanical fly by wire, as it is unstable.

For delta wings it's the opposite. Smaller delta wings turn more. Besides the su 35 the most maneuverable plane is the gripen. Delta wings have more speed. Otherwise they have worse low speed handling, more material, can't climb while turning, and have every disadvantage except the only factor that matters in dogfights, instantaneous turn.

As you can see the combination of technology (delta wing, thrust vectoring, relaxed stability) decide turn rate. The f 15 is a big partial delta wing, the gripen is a small one, and the su 35 is a big conventional plane with thrust vectoring.