Those are not really F-35 equivalents; they aimed for different points in the design space.

Both Russia and China cannot match the US on very low observable technologies, so they have tried to make the most low observable platform they could and then attempt the air combat problem with different technologies that they ARE good at. The J-20 has doubled down on having very long range, capable air to air missiles, as well as being highly datalinked with other Chinese platforms.

The Russians don't have nearly as good AAMs so they're just trying to be as maneuverable as possible.

I have a much higher opinion of the J-20 than I do the SU-57.