Quality vs Quantity,Some free worksheets are not good quality - the pictures are fuzzy, backgrounds print grey or speckled - and children tend to notice these things. If you are using the worksheets to educate your child, you may want to choose good quality worksheets that encourage your child to produce good quality work. After all, its a little difficult to ask your child to color within the lines and work neatly when the worksheet they are filling in hasnt done the same.
Kindergarten ABC worksheets should have different activities to help children identify the various letters of the alphabet. The activities may involve very simple things like colouring, ticking, drawing a line to match items etc. Using attractive illustrations and cartoon characters would make it more fun for children. The activities should be graded, i.e initial activities should be very simple and easy (but should be fun with good pictures etc, so as to interest the child); later worksheets may involve a little bit more work.