For general "fabulous" meaning amazing, excellent:
* Napakaganda (for something beautiful)
* Napakahusay (for something well-done)
* Napakasaya (for something joyful)
* Kahanga-hanga (for something impressive)
* Maganda (for something beautiful)
* Magaling (for something good)
* Galing (slang, similar to "awesome")
For "fabulous" in the sense of stylish or extravagant:
* Marangya (for something luxurious)
* Makatas (for something flashy, especially in a flamboyant way)
* Pambihira (for something unique)
* Nakasisilaw (for something dazzling)
The best word to use depends on the specific context and the intended meaning.