Even a photo that looks really nice on the screen looks 10 times better printed. The screen can't display the kind of resolution and detail that is really there. Especially for macro photography (my personal favorite), printing reveals details and beauty that, as far as I know, can't be seen in any other way.
I was pretty happy with this photo just seeing it on the screen. I know you've already seen it, and the detail on screen is great. But when I printed it, it looked insane. The details were as sharp and crisp as the real thing. Unfortunately, there's no way to show you how good it looked printed. You'll just have to try it yourself.
click to enlarge, or see it on Flickr
So experiment with printing some of your photos. If you have a nice color printer at home, buy a ream of high-quality paper and print them yourself. Otherwise, head over to the nearest Costco—their prints are ridiculously inexpensive, and process quickly.