17: 57. Those, whom they call on, themselves seek nearness to their Lord - even those of them who are nearest - and hope for HIS mercy, and fear HIS punishment. Surely the punishment of thy Lord is a thing to be feared. "
Recent human behavior studies concluded that Humans have TWO main motivators: Fear and Love. The study explained that without Fear, Humans won't be able to accomplish their daily regular tasks, such as: Work, Study, Sports, and even dining and sleeping. Humans fear hunger, so they work hard to get food. Humans fear failure, so they go to educational institutes to learn the knowledge and to succeed in their life. Humans, at least the Muslims, fear Allah, so they worship "ONLY" Him, in order to win the ultimate prize the Paradise. Muslims fear Allah, so they don't steel, Kill, Rape, etc.......
On the other hand, Christians & Jews have no fear of Allah, and bad deeds such as: Steeling, Raping, Killing, etc., are committed on a daily basis. So, the Christian argument that "Muslims have great fear of Allah" is 100% true. Fear of Almighty Allah is our main motivator to live righteous on Earth and to be awarded the great Heaven in the Hereafter.
Now, as far as Salvation, Christians say that in Christianity, one is saved by faith, whereas in Islam one must earn their salvation through good deeds. Unfortunately, many Muslims fall into the trap of defending the position imposed on them by these non-Muslims. This then provides the Christians with a basis for their entire Jesus-Father-Crucifixion-Salvation framework. They then go on to argue that salvation is a gift from God that cannot be earned. But if the true Islamic concept is made clear, the Christian has no basis to attack Islam.
Many times, Muslims fail to realize that the Islamic concept of salvation is not based upon good deeds, but is based primarily upon faith. In the dozens of times Allah (SWT) talks in the Quran about salvation, he always states, "Those who believe and do good deeds." Belief is always mentioned before deeds or works. When one converts to Islam, one does not do it by doing some good work but rather through realizing and believing that there is but one God and Muhammed (PBUH) is his last messenger. Non-Muslims may perform good works as well, but what sets them apart from Muslims is their lack of iman, or belief. The reason that the good works of the non-believers are worthless in the hereafter is because of their disbelief. Unless a person's iman or aqeedah is not correct, all his good deeds are worthless.
One of the more popular hadiths of the Prophet (PBUH) states, "All actions are based upon intentions," implying that the purpose, intent, or iman behind your action is what you get rewarded for, the actual action is really a consequence of the belief.
Another hadith states, "A man came to the Prophet (PBUH) and asked, "When will the day of judgment come?" The Prophet (PBUH) replied, "What have you prepared for the judgment day that you are so concerned for it?" He replied, "I do not have any good deeds in my account, but I do have one thing: I love Allah and His Messenger (PBUH)." The Prophet (PBUH) then said, "In that case, do not worry; you will be with those whom you love." (Agreed Upon). This hadith also confirms the Islamic position of placing aqeedah and belief before actions. For example, Allah (SWT) says in various parts of the Quran, "The believers you will find praying..." He does not say the people who are praying are believers. It is the belief that brings about the action, but the converse is not always true. Another hadith of the Prophet (PBUH) states, "Unless one loves Allah and Allah's Messenger more than one's own self his iman is not complete."
More accounts on Salvation:
Our great Prophet Mohammad (PBUH) said: " Whoever testifies that there is no God but Allah, and Mohammad is messenger of Allah, and Jesus is messenger of Allah, and His word has sent upon Mary and it was His soul, and Heaven exists (true), and Hell exists (true). Allah will let him enter Heaven from whatever gate ( among eight gates) he wishes, no matter what he did in his life." ( Bukhari & Muslim)
Prophet Mohammad (PBUH) said: " Whoever testifies that there is no God but Allah, and Mohammad is messenger of Allah. Allah has forbidden Hell (Fire) from touching him". ( Muslim & Tarmethy)