First you must understand how waterproof breathable products work. Breathable means that water vapor, or mist, can pass from the inside to the outside. Gore-tex is truly waterproof, but it relies on a layer of durable water repellent on the exterior (DWR). This DWR makes the water bead up and run off the jacket, but it only lasts so long. After extended periods in the rain the DWR stops working and the outside of the jacket gets wet. Note that the Gore-Tex layer is still waterproof, but with the wet exterior it is no longer breathable. At that point all the sweat from the inside can't get out, and it feels like the jacket is leaking.

DWR only lasts so many washes. Sweat, dirt, and regular detergent make it lose it's water repelling capabilities. Only wash with water or with specific detergent made for waterproof breathable articles of clothing. Heat helps to restore the DWR. Throw it in the drier or, even better, iron it. After so many washings or so much time you'll have to restore the DWR. You can buy products from ReviveX, Grangers, and others that will restore a DWR (only use fluoropolymer, not silicone).

As some people have said, some products breathe better than others, but it's usually a trade-off between waterproofness and breathability.