As often as I have to wash my oily hair, I use the cheapest baby shampoo I can find on the store shelf. I used to use the higher end shampoos designed for greasy hair, but I couldn't really tell much of a difference after one day. I think the shampoos themselves worked as designed, but I just have an especially oily scalp.
I use a conditioner after shampooing with the baby shampoo, and I make a point of leaving it in my wet hair for at least the time suggested on the bottle. I think some people with oily hair don't give their hair products enough time to work before they rinse them out.