It is easy for a person who feels less intelligent than others to have low self-esteem. This is unnecessary. While there are many advantages in having intelligence (for Torah study and other pragmatic reasons), when it comes to basic value of a person, intelligence is not a key factor. You can be righteous regardless of your intellectual ability. Similarly, intelligence is not a decisive factor in whether or not a person will be happy in life.
Since you can be both righteous and happy no matter what your level of intelligence, there is no necessity in feeling less of a person if others seem "smarter" than you.