The open rate depends on many factors such as your subject line, list quality and sending reputation.
Generally for purchased lists, an open rate of .5% to 5% is considered good.
For your own lists that are opt-in confirm the open rate of 15% to 20% is the average.
Keep in mind your open rate is actually higher than reported. This is due to the fact that we track opens using a tracking pixel and most email clients such as outlook disable the loading of images by default.