However, depending on the context you're using it in, here are some possible synonyms based on different interpretations of "sightful":
If you're using "sightful" to mean "having good eyesight":
* Sharp-sighted
* Keen-eyed
* Visionary
* Perceptive
* Observant
If you're using "sightful" to mean "capable of seeing or understanding things clearly":
* Insightful
* Discerning
* Astute
* Sagacious
* Perspicacious
If you're using "sightful" to mean "inspiring awe or wonder":
* Spectacular
* Magnificent
* Stunning
* Breathtaking
* Impressive
It's important to provide more context so I can give you a more precise synonym for "sightful." For example, if you could tell me how you're using the word, I can give you a better suggestion.