religionist: a person addicted to religion or a religious zealot
For the sake of argument, I would like to alter this definition a little:
religionist: a person who believes one must be involved in a religion in order to have a serious relationship with God, with significant preference given to their own religion
Obviously, most people who claim to be of a specific faith tend to fall into the "religionist" definition. Most religions include some kind of clause whereby you can only "find" God through that religion's "founder" (for example, Jesus or Mohammed) or through the religion itself (i.e. Judaism). So if you are not in that religion, you are out of luck, with the afterlife usually held over your head as your punishment for not going along with the flock.
So which religion is the right one? None of them, and all of them. It is NOT about which religion you pursue. It IS about your relationship with God. If you can find God through a specific religion, more power to you. The problem is that most people who find God this way seem to end up in the great pyramid scheme of religion, thereby becoming religionists. They assume incorrectly that, since they could not find God on their own, no one else can either.
Which brings us to the broader category of theism (also from Dictionary.com):
theism: Belief in the existence of a god or gods, especially belief in a personal God as creator and ruler of the world.
Admittedly, religionists far outnumber people who are just theists. Technically speaking, all religionists are theists, but not all theists are religionists. For example, there are also deists (from Wikipedia.org):
Deism is a religious philosophy and movement that derives the existence and nature of God from reason and personal experience.*
How can someone be a deist? Quite simply, look at the nature of the universe around you.
For example, the laws of physics are a beautifully scripted set of rules for how the universe works. While mankind may not have a complete understanding of these rules, they exist regardless. How did they come to be?
Another example can be found in nature. Nature works in a perfect balance. That balance may change, but it is never ruined. When a natural balance gets "upset", it will eventually return to normal over time. If a predator is introduced to an area where there were no predators before, you will see it completely dominate the area, possibly even causing some native species to become extinct. Yet eventually, that predator's population will drop if it over feeds, leaving itself without any food source, thereby allowing the native species to repopulate.
Consider the example of when the Earth's climate has warmed in the past, and the ice cover has receded, thereby allowing the Earth to warm even more since ice reflects sun light. Global Warming theorists point this out as some kind of never-ending spiral of Global Warming. Yet, that ice cover has always returned every time this has happened.
Too often, we look at the universe in a snapshot view, without looking at the processes at work over years, centuries, or millenia. But what maintains this balance? The atheist would view it as coincidence. The deist would view it as proof of God.
The deist knows that everything in the universe happens for a reason, even if we do not understand that reason. This is where religionists and deists agree. But there are other areas...
*The Wikipedia article also lumps agnosticism under deism, while I personally reject that definition. Deists DO believe in God, whereas agnostics claim God is unknown or unknowable. How could one derive "the existence and nature of God" if God is unknown or unknowable? Therefore, as I see it, there are three overall views as to the existence of God: theism, agnosticism, and atheism.