General joy:
* Joy
* Pleasure
* Happiness
* Gladness
* Exhilaration
* Rapture
* Ecstasy
* Thrill
* Bliss
* Contentment
Stronger, more intense feelings:
* Enchantment
* Rapture
* Ecstasy
* Euphoria
* Transport
Informal terms:
* Fun
* A kick
* A blast
Other possibilities:
* Gratification
* Satisfaction
* Amusement
* Enjoyment
The best synonym will depend on the specific nuance you want to convey. For example, "delight" might be used to describe a feeling of gentle happiness, while "ecstasy" would be used for a much more intense and overwhelming feeling.