General opposites:
* Cheerful
* Comforting
* Familiar
* Friendly
* Inviting
* Normal
* Pleasant
* Safe
* Welcoming
Specific to specific eerie situations:
* Bright (opposite of dimly lit)
* Calm (opposite of unsettling)
* Natural (opposite of unnatural)
* Ordinary (opposite of strange)
* Peaceful (opposite of frightening)
The best antonym will depend on the specific context in which "eerie" is being used.