Fruit trees need a lot of sunlight to really produce. Otherwise you'll get stunted fruit that's susceptible to a number of diseases and blights, plus the fruit is usually smaller and has less sugar content. There are hardy hybrid peaches that are supposed to grow here, but I've always thought the few I've eaten weren't all that good. I opted for apricots. Huge producer of fruit; the fruit is super sweet, easy to prep and can/freeze, and the trees are fairly easy to maintain.
Are they self pollinating? What hybrid/type did you get?