I think that there are many facets to Johnny, and that we see how given the right opportunity he could be so much more than his life has given him the opportunity to be. I think that when he saves the children from the fire he is at his most alive. It is an adventure where he is the hero, instead of being the peretual victim which has been his past. This is certainly the event which I think Johnny would like to be remembered for, and it is perhaps where we begin to understand Dallas Winston's deep appreciation and admiration for Johnny stems from.
I agree with number 3. When Johnny and Ponyboy are on the run, they learn more about each other. I like their reaction to the book and the poem. I think it shows that Johnny wants to change. He is very sensitive, and he's had a hard life. We feel for him in this moment.
For me, it is when he and Ponyboy are hiding out in the church. We particularly see Johnny's personality when they are reading from Gone With the Wind. This is not at all what you would expect a person like him to enjoy. We learn from that about his sensitive personality and his romantic/idealistic streak.
For me, the personality of Johnny Cade is actually revealed most when Ponyboy reads Johnny's final letter to him at the end of the novel. This might be a rather strange way of answering your question, but let us remember that before this, Johnny is a man who is plagued by a series of demons, as his character shows. The memories of being beaten up by Socs, the relationship he has with his mother and his own insecurities make him a man who "jumps at his own shadow" in the words of Ponyboy. What is really interesting about the final missive he leaves for Ponyboy is the way that we see a Johnny who has, to a large extent, accepted so many of these tensions and is at peace with himself and his imminent death. Note what he says:
The doctor came in a while ago but I knew anyway. I keep getting tireder and tireder. Listen, I don't mind dying now. It's worth it. It's worth saving those kids. Their lives are worth more than mine, they have more to live for.
We see at the end of the novel a Johnny that is able to see his actions and his life in context. He reveals the kind, caring, and loving individual that he always has been throughout the novel, but has been hidden underneath many different kind of masks thanks to his social situation and his experiences.
for me its when he was at the movies and he spoke up for the first time