General synonyms:
* Well-liked
* Favorite
* In demand
* Trendy
* Fashionable
* Common
* Prevalent
* Widespread
* Ubiquitous
* Celebrated
Synonyms related to specific contexts:
* Famous (for people or things)
* Renowned (for people or things)
* Celebrated (for people or things)
* Highly regarded (for people or things)
* In vogue (for fashion or trends)
* Beloved (for people or things)
* Adored (for people or things)
* Trendsetting (for people or things)
* Mass appeal (for products or ideas)
* Mainstream (for media or culture)
* Sought-after (for products or services)
The best synonym will depend on the specific meaning you want to convey.