On my own personal experience, when I was younger, hard-core atheism always struck me as the best match. Not just because of personal belief but because after a whole ten years of constant education in a catholic school it's not uncommon to see someone rowing in the opposite direction. As life progressed and troubles accumulated without any real change or turn of course, you tend to doubt what you thought you knew. The stimulus progressively gets better as you start to take matters into your own hands and do not directly correlate it with religion, so you can say, "Why do I need god when I have myself?"
However everyone keeps growing, I was inmature. Things usually do not tend to go the way you expected it and spiritualism suddenly becomes a heavier weight on your consensus. Everyone has experienced the loss of people you love, and, while you could boil it down to the simplest of routes - which is of, well, how physics behave and how we are just chemistry - it doesn't sit right with you. Even less when you hear for example testimonies of other people who have had traumatising losses, or family. It really did widen my eyes to broader horizons which I thought were explored, but in reality, were quite obscure.
Even then, I still don't believe in God, it is hard for me to come to grips with catholicism. I probably never will. Even when I was, it was a very cold relation, it was more pinned to educational religion than faith. Of course, everyone has their low points where they start to doubt; I used to visit these grandious churches and cathedrals while on vacations, seeing whatever figures that are built to evoke emotion in you, the glittering and the music, the sudden sensation you're in a place thought sacred. Reading, experiences, hearing what people has to say. Even when going to the smallest of churches, trying to rationalise it, whatever.
But, no. Doesn't suit me. I'd say that is not really the essence of say, christianism. Specially when you see such a shallow practice around you, it is a very watered down version of what I thought it was.
Instead I tend to have more of a very marginalsied agnostic position, as many others in the thread, that ties with atheism. There is open room for spiritualism. I do not necessarily think that one God exists, but that life in itself isn't just a shallow chained path of events dictaminated by what we're made of. For me a realer religion is humility, live with yourself and others, strive to become something better that comes from yourself, not the man above or the book under the counter. I've lived Christianism, I still live it because I live in a culture ingrained with it, and for me, going to a church, confessing my sins to the priest, it makes no sense. God isn't in him, and if someone has to hear me, it is me, with myself, anywhere.
It helps one to investigate in other religions such as Islam and the old paganisms of Europe, the history is there, I embrace that. But a healthy view is to respect those who believe, I find them to be just as worthy as anyone else, and I find it a very respectable aspect of life, but if they believe, I really hope it is a honest belief.