Yes...though moving to Israel doesn't necessarily require a Jewish parent. It is possible to move there as a non-Jew. That's harder than Aliyah/right of return, but worth mentioning.
From what you've provided, you may be able to make the case for moving to Israel under the right of return. A general rule is that you need one Jewish grandparent to make Aliyah, and you'd have that even if grandpa wasn't that religious. One thing that may negate your claims is if your great-grandmother converted out of Judaism before giving birth to him, or if you can't prove your grandparent or great-grandparent was Jewish. To take advantage of the right of return/Aliyah, Israel will need certain documents (e.g., marriage certificates or death records) or backing from a respected individual like a Rabbi to confirm your Jewishness.