You should keep this in mind: most people reject the God taught by religion. That people have their reasons for not believing in God. Some things that you could say is that while other people may die for their god, our God is the only one who died for people (I'm not sure if that is entirely true, but then again I don't study anything but Christianity
), or that we pray to the only living God.
Faith comes by hearing, and hearing by the word of God. Ever wonder why Jesus said after a parable, "He who has ears to hear, let them hear!"? It sounds like you're telling them the Word, though...
It can be a bit depressing, but don't lose heart.
I recently witnessed to an atheist a couple days ago (I've known him for a while and he came at me every time I mentioned Him and he ridiculed Him), and I did all of the things below and then some (the day I witnessed to him). Not to say that there wasn't other things that helped, or that those below helped completely, but I wasn't doing some hit and miss tactic:
The only thing you can do is pray, if they aren't listening to you. If I could explain this better, or give any explanation, I would, but here's what I do:
I pray in the name of Jesus and, while using authority, I command the blinders to go
[<-- what I should have done there is bind the demonic influence, sorry] and that person's heart to soften, and I remit their sins in Jesus' name. Then I pray that a spirit-filled believer talks to them, and that they'll listen. I also asked God to tell me what to say.
I countered the religious teachings of God, answered the things he threw at me, and now he says that he knows who to talk to about any matters relating to God. The only thing with the things I have said above this paragraph is that the way I figure it is that person has 95% influence on them self. You may have to keep commanding the blinders go and that their heart be softened and that more workers go in. You also have to remember that 95% of any one person is their own influence. It's ultimately their choice.
I'll get back to you on this with some sort of an explanation for why I did what I did + the Scriptures.