My current favorite rain gear is home-made of non-breathable silnylon. It's a simple anorak, weighs 3 oz and packs the size of a fist. I have matching pants, but seldom use them while cycling. Maybe on a mountain pass descent in wet snow, or something extreme like that.

What's at least as important as the outer layer is how you use the rest of your clothing. An old pro with a plastic poncho and wool sweater can often be more comfortable than a newbie with the latest laminates and tech fabrics. If you wear your breathable jacket over all your insulation while climbing in the rain, you'll quickly wet everything out and you'll be miserable on the descent.