I believe that in today's society we do not give fathers enough credit. We tend to focus on the shortcomings of a man and not the heart of the man. I will agree that it is very difficult to see the good in a man who refuses to support his children's emotional, financial, physical, and spiritual growth. I also find it extremely difficult to respect a man who does not respect the mother of his children. You will notice that I did not say it is impossible, only difficult.
For many years I resented the lack of effort my father put into my upbringing. I hated the way he treated me and my sister (in comparison to his g/f's kids) and how my parents always managed to stir up an argument every time they saw each other. Regardless of how mad I was at my dad, he always managed to be there for the most important days of my life. He never missed a graduation, my wedding, buying our first home, or my daughters birth. I had to learn to forgive him and not focus on what he wasn't doing, but rather admire the strength it took to be there when I needed him the most.
Likewise, he doesn't allow my shortcomings to dictate his love for me. Instead he loves me unconditionally. Regardless of how long it takes him to get there, or how he stays. What's important to me is that I can always count on him to be in my cheering section, sometimes with the loudest cry. I love my daddy.
If nothing else, I hope you will learn to focus on the things fathers do right, instead of always criticizing them for what they do wrong. He may not be on time to every birthday party, but if he remembers to call or come, gift him credit. He may not know how to fix a flat tire or put a band-aid on a boo-boo, but if he wipes 1 tear, give him credit. He may not approve of your lifestyle choices, but if he still comes to your house, give him credit for trying. It's tough being a father. Don't take it away because he isn't you. It's not always the big moments that matter, but the small things he does to show he loves you and your children.