In the Silabbata Sutta, the Buddha asked his disciple Ananda whether every holy life is fruitful. Ananda responded (which was ultimately praised by the Buddha) that if one's holy life of precept and practice results in one's unskillful mental qualities increasing and one's skillful mental qualities declining, that practice, that holy life, is unfruitful. He continued that a practice in which one's skillful mental qualities increase and unskillful mental qualities decrease, that is a fruitful path.
What did Ananda mean by skillful and unskillful mental qualities? Well, the Abhidhamma, a compendium of Buddhist psychology, goes into complete detail. But, honestly, you can use your common sense and get it mostly right. A few examples of unwholesome qualities: shamelessness and fearlessness of wrongdoing, greed, hatred, conceit, sloth, worry, etc. A few examples of skillful, or wholesome, qualities: faith, mindfulness, compassion, love, appreciative joy, etc.
1-Minute Contemplation: Take a moment to reflect on your chosen path. Does your path have a name like Buddhism, Christianity, or Wicca? If not, no matter, it does not need one. Do your spiritual practices, be they prayer, meditation, writing poetry, communing with nature, or communing with a pantheon of gods & goddesses, result in an increase in skillful mental qualities and a decrease in unskillful ones?
If your practices are fulfilling the criteria described by Ananda, then you are on a fruitful path. If not, then perhaps you should re-examine your path. If you are Christian, but find that your practices are not improving your skillful qualities, that is not reflective of Christianity (as others have greatly benefited from that tradition), but rather is reflective of the fact that Christianity just may not fit your mental disposition. Just as diversity in species is required for the Earth's ecosystem to survive, diversity in religion is required for the many dispositions and personal experiences of people in the world.