I should say this is an interesting question to ask. I have different insight on this matter. I met in my life with many religious people are spent also time with spiritual people. Few of them were not Muslim. Some of them were Buddhist, some of them were christen and some of them were looking for truth.
There was one common quality among all spiritual people, they were very peaceful people. Everyone has his own thinking about peaceful life and how he should behave with other people. All the non Muslim spiritual people were confused in many aspects of life. They were looking for truth but were not sure about their beliefs.
Islam gives the highest level of spirituality. Every Muslim is somehow spiritual but when a Muslim practices the Islam with its true understanding everyday he is actually increasing his spiritual station.
Following are few Ahadis of Rasula?Allah (S.A.W).
1- The one who knows himself knows his Lord
2- One hour of thinking is better than the worshipping of 70 years. (It shows that how important mediation is in Islam. Meditation is one of the pillar of spirituality)
3- This is the Hadis-E Qudsi. Who seeks ME finds Me, He who finds ME knows ME, he who knows ME loves ME, he who loves ME, hey MY love.
RasulAllah (S.A.W) was on the highest level of spirituality and everyone who wants to enter in the spiritual world first become muslim and must follow the teachings of RasulAllah (S.A.W). There is no other way to enter in the spiritual world.
I hope, these few words will help to show the spiritual side of islam. Insha?Allah
May Allah forgive me and bless all of you for the honor of the most honor one in His divine presence Sayadina Muhammed (S.A.W).
As for the person who asked for my opinion the subject:
Religious people are afraid of going to hell vs. Spiritual people they have already been their to hell. Meaning that they have seen it all on this earth from pain, suffering, injustice and so on and still standing accepting and/or dealing with it on a daily bases while still having the faith in God by showing love and acceptance and treating others humans with acceptance and respect by taking out the judgment and being responsible and holding only their self to judge and reflect. To be and show-up in peaceful mod regardless the turmoil of our surroundings.