Just like retirement savings goals, it entirely depends on the family and what they value. There is one key factor that I like to remind my clients: Your kids can borrow money for college, while you cannot borrow money for retirement. Remember that.
The parents' (or parent's) obligation is to ensure that they are self sufficient in retirement. If you don't plan appropriately to take care of yourself in retirement, you could ultimately become a financial burden on your children.
If funding their education is that important to you, you could still have them take student loans and commit to repaying them, on their behalf. The point is, there are options for financing college - there are no good financing options for your expenses in retirement.
Once you are on track to meet your retirement needs and/or goals, then it is fully appropriate to investigate college savings options, if that is something you plan on giving to your child(ren). So, whether your son or daughter is fortunate enough to have this weight lifted from their shoulders, or they have the opportunity to learn first-hand how much these four, five, or six plus years cost, make sure YOU invest well!