Kodak Medium Format Slide Projector Why Do Pictures Look Better Before I Get Them Printed??

Why do pictures look better before I get them printed?? - kodak medium format slide projector

Take advantage of many digital photos and I think they look great on the camera and computer, I print them in 4x6 and never so good! When I printed oblong and slightly blurY and color is a little further! When printing to do, even like the pictures are from the outside world a bit stretched at the edges and then a 4x6 fit! Why and how do I solve this problem? I take photos in the middle of 2 (1600x1200) is too large, too small or the right size to have it printed as a 4x6? I have not printed them on the Kodak Picture Maker at Walmart and walmart.com on snapfish.com! Thank you!