This (and similar verses as in the title) should never be taken out of context in order to distort the Gospel. Therefore we must first go to the Gospel itself and then see how these fit. In another thread, a brother posted John 3:16-21. So we should go from John 3:15 to 3:21 (plus verses 35 & 36):
JOHN 3: THE GOSPEL ACCORDING TO THE LORD JESUS CHRIST
THE BRAZEN SERPENT WAS A TYPE OF CHRIST
14 And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:
"WHOSOEVER" MEANS ANYONE AND EVERYONE, AND INCLUDES ALL
15 That whosoever believeth in him should not perish, but have eternal life.
GOD'S LOVE EXCLUDES NO ONE
16 For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
GOD'S LOVE INCLUDES THE WHOLE HUMAN RACE
17 For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
FAITH IN CHRIST IS ABSOLUTELY ESSENTIAL
18 He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
SOME MEN CHOOSE DARKNESS OVER LIGHT
19 And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
EVILDOERS HATE THE LIGHT OF CHRIST AND OF THE GOSPEL
20 For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
THOSE THAT CHOOSE TRUTH COME TO CHRIST
21 But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God...
GOD THE FATHER HAS GIVEN CHRIST ALL AUTHORITY IN HEAVEN AND ON EARTH
35 The Father loveth the Son, and hath given all things into his hand.
THOSE WHO BELIEVE ON CHRIST RECEIVE ETERNAL LIFE
36 He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.
In view of this passage, the ones who hate the light of Christ and of the Gospel are barred from coming to Christ. Thus the Father grants that only those who believe and obey the Gospel will come to Christ and receive eternal life.