General:
* Excellent
* Great
* Wonderful
* Fine
* Nice
* Pleasant
* Satisfactory
* Acceptable
* Decent
* Suitable
* Positive
* Favorable
More specific:
* For quality: High-quality, superior, first-rate, top-notch, exemplary, outstanding
* For taste: Delicious, tasty, flavorful, palatable, savory
* For behavior: Kind, virtuous, moral, ethical, righteous, honorable
* For health: Healthy, well, strong, robust, fit
* For luck: Fortunate, lucky, auspicious, prosperous
* For appearance: Beautiful, handsome, attractive, lovely, charming
* For feeling: Happy, joyful, cheerful, contented, satisfied
Informal:
* Awesome
* Cool
* Rad
* Sweet
* Brilliant
* Amazing
The best synonym for "good" will depend on the specific situation and the intended meaning.