"It seems by the way Jesus told the story, that one need not be a christian to inherit eternal life. "
True, by the parable alone it does seem that way. But remember the context. The original question was in verse 25 where a teacher of the law tests Jesus:
"Master, what have I to do that I may have eternal life?" (BBE)
Then Jesus gets him to answer his own question in verse 27:
"Have love for the Lord your God with all your heart and with all your soul and with all your soul and with all your strength and with all your mind; and for your neighbour as yourself." (BBE)
Jesus basically says 'yep, that's it.' And then I think the teacher feels a bit embarassed so he asks "And who is my neighbour?" (BBE) Jesus responds with the parable of the Good Samaritan.
All that to say: The parable of the Good Samaritan does not answer "How shall I have eternal life?" It answers "Who is my neighbour?"
In regards to eternal life, I think anyone who believes that Jesus Christ is the Son of God, came to Earth and died for our sins would agree that part of loving Him includes accepting the forgiveness He offers us and following Christ and His teachings.
Jesus did say "judge not, lest you yourself be judged." But He also said "I am the Way, the Truth and the Life. No one gets to the Father except by Me."
Please let me know if you believe I've left something important out or misinterpreted something.