There's absolutely nothing wrong, of course, with wanting all your kids in this world to do equally well. In the life of a proud parent, it's just another day. Unfortunately, for one cause or another, in the majority of households, not every child is created equal. Some kids can also struggle with a physical or mental disability, have a problem with drug abuse or something else that is equally difficult.
That being said, the standards for every family member in your household can be changed... even for grown-ups. Other parents are doing this effectively.
It's incredibly important not to equate one child against another when defining your children. It's also necessary not to try to fit them into a mold. On this world, every child is different. No two kids will ever be exactly alike when it comes to stuff like thoughts and accomplishments.
Take the appropriate time to really reflect on each of your kids. Forget about what their friends are doing, forget about what you've read online or on TV, and forget about what your spouse or partner is saying.