“Good” varies widely across industries as every business will have a different profit margin to base success on, and you may have products in different marketing stages. You may also have different versions of “good” depending on the channel on which you’re running the activity.
Return-on-ad-spend (ROAS) has long been used as a measure of campaign performance and profitability when it comes to PPC and paid social.
The ROAS number in isolation is never a measurement of success or failure. What ROAS means in terms of actual profitability is what the vast majority of advertisers should consider.