IIRC, Ted was born in Canada, to parents who are US citizens. That would make him a natural born US citizen, and therefore eligible.
Cruz's father was NOT a US citizen when Cruz was born.
from wikipedia:
The elder Cruz worked his way through college as a dishwasher, making 50 cents an hour,[19] earning a degree in mathematics.[25] Cruz's father today is a pastor in Carrollton, Texas,[18] a Dallas suburb, and became a naturalized U.S. citizen in 2005.
