General:
* Common
* Ordinary
* Standard
* Typical
* Universal
* Non-specific
* Unspecialized
* Unbranded
Related to Products:
* Off-brand
* Store-brand
* No-name
* Plain
* Basic
Related to Language:
* Vague
* Unoriginal
* Uninspired
* Banal
The best word to use will depend on the specific meaning you want to convey. For example, if you're talking about a product, "off-brand" might be a good choice. If you're talking about a concept, "general" or "universal" might be better.