All scriptural quotes are from the World English Bible unless otherwise noted
The Bible tells us that God is love (1 John 4:8,16), and that Love is the greatest of all things – even better than spiritual gifts (1 Corinthians 13:1-3, 13). As the Bible readily shows, not only are we to have love among ourselves (John 13:34), but we are to display love towards our enemies as well (Matthew 5:43-46, Luke 6:27). Real love includes showing love towards strangers (Luke 10:30-35). Our love must be without hypocrisy (Romans 12:9). Real love never shows favouritism (James 2:8). In other words, genuine love is unconditional and is given without stipulations.
DEFINING UNCONDITIONAL LOVE
The Bible describes the state of real, unconditional love at 1 Corinthians 13:4-8:
(4) Love is patient and is kind; love doesn’t envy. Love doesn’t brag, is not proud, (5) doesn’t behave itself inappropriately, doesn’t seek its own way, is not provoked, takes no account of evil; (6) doesn’t rejoice in unrighteousness, but rejoices with the truth; (7) bears all things, believes all things, hopes all things, endures all things. (8) Love never fails....
You can't describe it any better than that! And, since God is Love, and real love is unconditional, this would have to mean that God's love is unconditional.
THE BIG QUESTION
Unfortunately, some disagree with this reasoning. Such people take the position that, if God's love were truly unconditional, then mankind shouldn't be forced to live by certain requirements, such as having faith in Christ's Blood (Romans 3:24-26), acting on that faith (James 2:14-17), and keeping Christ's commandments (John 15:14) in order to obtain Salvation. However, since these requirements exist does this mean that God's love is actually conditional?
Although God's love is unconditional, this doesn't negate the fact that sin cannot stand in the presence of God (Habakkuk 1:13, Isaiah 35:8-10, Revelation 21:27). Sin is what separates us from God (Isaiah 59:2). The only way to remove the sin is by way of a covenant, and covenants can only be inaugurated through blood (Hebrews 9:16-22). Jesus Christ's blood sealed the New Covenant (Luke 22:20), which is what removes the sin that separates us from God. This is why Scripture says that we are washed clean by His blood (Revelation 1:5, 7:14). Without the gift of Christ's blood nobody could stand clean in God's presence; none of us could be saved.
Because God offers mankind unconditional love, He sent Jesus Christ to Earth in order to give us a chance at this Salvation (John 3:16-18). The only problem is, if a person doesn't believe in Jesus Christ, that person automatically doesn't believe in the New Covenant He inaugurated. Since the only way to be washed clean of sin is by faith in Christ's blood, such non-believers remain unclean in their sin because they do not accept this blood-launched Covenant (Hebrews 10:29-31). This is what precludes them from being clean enough to stand in the presence of God, thus barring them from the hope of Salvation.
UNCONDITIONAL LOVE VS. FREE WILL
This is where the concept of Free Will comes in. Every person who comes in contact with the Gospel of Christ has a choice of free will: They can either choose to accept the Gospel and be saved, or choose to reject the Gospel and remain damned (Mark 16:16). Because God wants us to love Him voluntarily He doesn't force us to choose one way or the other in spite of the fact that He desires every person to come to salvation (1 Timothy 2:3-4).
This situation can be likened to a blood transfusion:
Say your neighbor is in a major accident and will die without a blood transfusion. You have a compatible blood type so as an act of unconditional love you offer a pint of your own blood to save him. Your neighbor happens to be a member of the Jehovah's Witnesses (a denomination which refuses these kinds of transfusions on doctrinal grounds), and thus refuses the transfusion, resulting in his death. Your gift borne from unconditional love could have easily saved him; but it was his own refusal to receive that gift that doomed him. His death is not on your head for you freely offered the gift of life; it is the victim's own fault for refusing your free gift.
Likewise, God has offered us the life saving blood of His Son to save us from the deadly hemorrhage of sin. It is an individual's own refusal to accept this free blood that kills him; not a loveless requirement from God. Just as a doctor cannot force a Jehovah's Witness patient to accept blood, God cannot force non-believers to accept Christ's blood.
Although the requirement for belief in Christ may be misunderstood as conditional love, it is clear that such a requirement is actually evidence in favour of unconditional love! Because God is the personification of true, unconditional love, He couldn't let us continue on without a way towards Salvation (for to do otherwise would be unloving). He recognizes that sin is spiritually bleeding us to death and so He lovingly offers us a free cure for this; it is up to each individual to accept this cure, or to refuse it. Giving us a cure, along with the free choice whether to accept it, is clear evidence of God's unconditional love.
May our God and His Christ give you peace on this matter.