Martin said:
It's like Pado said, if you're a believer, that's enough in itself. You don't have to go to church to prove anything to yourself. You can never go to church and still be very devout.
You
can believe without going to church. But that means faith becomes something individual. Many believers agree that faith has both an individual side (praying, being a good person,...) and a community side (mass, sacraments, evangelism, converting,... proselytism?).
Jesus barely talked to individuals in the gospels, he preferred talking to the 12, or even better, to large groups of people. I think christianity has a vocation for being universal. Every true christian (and probably muslim also) hopes somewhere that the whole world would one day believe in God. But except for some extremists, all agree that faith can only mean someting if it's based on free will. Forcing someone to believe is a total absurdity. Hence the stupidity of proselytism, but not of evangelism (converting).
Protestants are more individualists than catholics, as they believe everyone should read the Bible and make up for his own what to do with it. The minister would only be a help, but should not tell you what to think. Catholics on their side have a far more hierarchical system, and the believers have to believe what the authority tells them to believe. But notice that protestants also go to church and listen to the minister... Every religion has it's rituals, in order to gather people and to unite them around their religion.
I guess it's just a question of definition. You can of course believe without listening to anyone, nor gathering with anyone for that purpose. But IMO you can't call yourself religious, as this implies that you are a 'member' of a religion.