Christians, do you believe decent non-Christians will go to Hell forever?

I think you have a hard time understanding because you don't understand the nature of Hell. God does not torture people who go to Hell. In the end, God will create a new world. In this world, everyone will be in total communion with God. Those who do not want to be in total communion with God would only cause problems for the new world, and forcing people to be in total communion with him is not something God wants to do. So, those who do not want to be part of the new world are not made to. They, instead, get to stay in the old world, which is to be forgotten by God. Since God will have left, the devil will have moved in, since, where God is not, there is the devil. So, the earth will become part of Hell, in complete separation from God. God is not torturing people by allowing them to choose to be separated from him. They are choosing to separate themselves from God. Since they don't want to be in total communion with God, their only option is the complete separation from God that will be the case after the end of time, and is currently the case in the fires prepared for the devil and his angels that is Hell.

So, the person who is a "good person in life" is not a good person in spirit, and through their own choice they detach themself from God, choosing the alternative: Hell. Doing the right thing and being a good person in life are part of being a good person in spirit.