General synonyms:
* Cohort
* Age group
* Era
* Period
* Epoch
* Time
* Age
Specific synonyms:
* For offspring: progeny, descendants, issue, lineage
* For a group of people born around the same time: cohort, age group, peer group
* For a specific time period: era, period, epoch
* For a technological advancement: innovation, development, breakthrough, leap
The best synonym for "generation" will depend on the specific context of your sentence.