SB 11.9.28

sṛṣṭvā purāṇi vividhāny ajayātma-śaktyā
 vṛkṣān sarīsṛpa-paśūn khaga-dandaśūkān
tais tair atuṣṭa-hṛdayaḥ puruṣaṁ vidhāya
 brahmāvaloka-dhiṣaṇaṁ mudam āpa devaḥ
Synonyms: 
sṛṣṭvā — having created; purāṇi — material bodies that house the conditioned souls; vividhāni — many varieties; ajayā — through the agency of māyā; ātma-śaktyā — the Lord’s own potency; vṛkṣān — trees; sarīsṛpa — reptiles; paśūn — animals; khaga — birds; danda-śūkān — snakes; taiḥ taiḥ — by all these different varieties of bodies; atuṣṭa — unsatisfied; hṛdayaḥ — His heart; puruṣam — the human form of life; vidhāya — creating; brahma — the Absolute Truth; avaloka — vision of; dhiṣaṇam — intelligence suitable for; mudam — happiness; āpā — achieved; devaḥ — the Lord.
Translation: 
The Supreme Personality of Godhead, expanding His own potency, māyā-śakti, created innumerable species of life to house the conditioned souls. Yet by creating the forms of trees, reptiles, animals, birds, snakes and so on, the Lord was not satisfied within His heart. Then He created human life, which offers the conditioned soul sufficient intelligence to perceive the Absolute Truth, and became pleased.
Purport: 

God has specifically created the human form of life to facilitate the liberation of the conditioned soul. Therefore one who abuses human life prepares his path to hell. As stated in the Vedas, puruṣatve cāvistarām ātmā: “In the human form of life there is good possibility of understanding the eternal soul.” The Vedas also state:

tābhyo gām ānayat tā abruvan
 na vai no ’yam alam iti
tābhyo ’śvam ānayat tā abruvan
 na vai no ’yam alam iti
tābhyaḥ puruṣam ānayat tā
 abruvan su-kṛtaṁ bata

The purport of this śruti-mantra is that lower forms of life, such as the cow and horse, are not actually suitable to fulfill the purpose of creation. But human life awards the opportunity to understand one’s eternal relationship with God. Thus, one must control the material senses and fulfill the real purpose of human life. If one takes to Kṛṣṇa consciousness, the Supreme Lord personally feels happiness and gradually reveals Himself to His devotee.

The Lord’s material creation consists of the living entities and dead matter, which the less intelligent try to enjoy. The Lord, however, is not satisfied by those species that blindly strive for sense gratification without understanding spiritual nature. We are suffering due to our forgetfulness of Kṛṣṇa and the blissful situation of His abode. If we accept the Lord as protector and shelter and execute His order, we can easily revive our eternal, blissful nature as parts and parcels of the Personality of Godhead. It is for this purpose that the Lord has created human life.