"I agree that Jesus was a good man, and a wise leader, but I don't think he was God!"

Koran Sura (Chapter) 5 verse 78 "Christ, the Son of Mary, was no more than an apostle."

This isn't one of the possibilities!  Jesus was either:

• LORD

• LIAR    ... or ...

• LUNATIC
  

Jesus claimed to be God.

LIAR

If Jesus wasn't God, and if He knew He wasn't God, then He was a LIAR  who knowingly and intentionally led hundreds of millions of people away from Jehovah, which would result in their eternal damnation.  No matter how "nice" or "wise" such a person might appear, knowingly leading millions to damnation can't be considered "good."  Such a person can't possibly be "an apostle" of God.
 

LUNATIC

From the Bible it's pretty clear that Jesus thought He was God and claimed to be God.  He claimed that the whole world revolved around Him.  He claimed He was the only way to be saved and that He spoke for God and as God.

John 14:6   Jesus answered,"I am the way and the truth and the life. No one comes to the Father except through me.

If Jesus believed He was God but He wasn't, THEN HE WAS A LUNATIC!

Obviously, a lunatic would have no problem claiming he can do miraculous things.  But Jesus backed up His claims with results:

Raising Jairus' daughter from the dead.

Mark 5:21-23, 35-42   [21] When Jesus had again crossed over by boat to the other side of the lake, a large crowd gathered around him while he was by the lake. [22] Then one of the synagogue rulers, named Jairus, came there. Seeing Jesus, he fell at his feet [23] and pleaded earnestly with him, "My little daughter is dying. Please come and put your hands on her so that she will be healed and live."

[35] While Jesus was still speaking, some men came from the house of Jairus, the synagogue ruler. "Your daughter is dead," they said. "Why bother the teacher any more?" [36] Ignoring what they said, Jesus told the synagogue ruler, "Don't be afraid; just believe." [37] He did not let anyone follow him except Peter, James and John the brother of James. [38] When they came to the home of the synagogue ruler, Jesus saw a commotion, with people crying and wailing loudly. [39] He went in and said to them, "Why all this commotion and wailing? The child is not dead but asleep." [40] But they laughed at him. After he put them all out, he took the child's father and mother and the disciples who were with him, and went in where the child was. [41] He took her by the hand and said to her, "Talitha koum!" (which means, "Little girl, I say to you, get up!"). [42] Immediately the girl stood up and walked around (she was twelve years old). At this they were completely astonished.

Healing centurion's servant at a distance

Matthew 8:8,13  [8] The centurion replied, "Lord, I do not deserve to have you come under my roof. But just say the word, and my servant will be healed."  [13] Then Jesus said to the centurion, "Go! It will be done just as you believed it would." And his servant was healed at that very hour.

Walking on water

John 6:19 When they had rowed three or three and a half miles, they saw Jesus approaching the boat, walking on the water; and they were terrified.

Controlling the weather

Mark 4:37-41 [37] A furious squall came up, and the waves broke over the boat, so that it was nearly swamped. [38] Jesus was in the stern, sleeping on a cushion. The disciples woke him and said to him, "Teacher, don't you care if we drown?" [39] He got up, rebuked the wind and said to the waves, "Quiet! Be still!" Then the wind died down and it was completely calm. [40] He said to his disciples,"Why are you so afraid? Do you still have no faith?" [41] They were terrified and asked each other, "Who is this? Even the wind and the waves obey him!"

Healing leprosy

Mark 8:2-3 [2] A man with leprosy came and knelt before him and said, "Lord, if you are willing, you can make me clean."  [3] Jesus reached out his hand and touched the man. "I am willing," he said. "Be clean!" Immediately he was cured of his leprosy.