Three obvious criteria immediately spring to mind:
1) science fiction stories written by Filipinos;
2) science fiction stories written in Filipino; and
3) science fiction stories with Filipino protagonists
We could quickly and vigorously assent to these concretely qualifiable distinctions and be done with it. But such simplistic definitions are feel shallow and unsatisfactory: they stem from mere accidents rather than from the core essence.
Suppose a Filipino writes a compelling and scientifically feasible story about the society of our evolved human descendants, say, in the year 40,000. The setting is so far into the future that, if the story is well-written, there would be no traces of existing cultural idiosyncracies. There would be nothing uniquely Filipino about the story other than its authorship. If this is the only criteria to call this science fiction story Filipino, then we're done.
Authorship alone isn't as neutral as we think, however. The problem with the year 40,000 is that its too far off as to be safe and sterile. If we bring the time frame closer to the present, we'll find that nationalist sentiments, no matter if they're misplaced, eventually come to play. A Filipino who writes a well-researched and well-executed story about American scientists fighting an alien virus in New York City will likely be derided by his peers as derivative.
Suppose, then, that that Filipino writer rewrites his story in Filipino, Filipinizes all his protagonists, and relocates the alien virus outbreak to Makati. The translation does not add anything new to the story. His characters and setting will simply be tacked on. Worse, the story loses its authenticity to Filipino readers who, in general, think so little of their country's own scientific and technical capabilities.
This lack of confidence in Filipino scientific capability is perhaps the reason why what few Filipino science fiction stories there are often encroach into the territory of fantasy for their plot devices. Some Filipino writers justify this shortcut on account of our supposedly dismal science education, but this is a lame excuse for poor storytelling. Scifi stories that were part physics and chemistry lessons had their heyday in the juvenile literature by Asimov and Heinlein. These days, its sufficient for the science to be plausible only as far as to support the readers' suspension of disbelief.
Science fiction, after all, is not about the science but about the fiction. Good fiction comes from good plot, good narrative, and ultimately, good characterization. Good fiction has something to say about the human condition. It may use an alien virus as an allegory for our primal fear of death and disease; it may use our descendants in the year 40,000 from now as stand-ins for us to reexamine our notions of justice and mercy.
Good science fiction uses some jarring strangeness, explainable by science, to put the human condition into stark relief.
Applying that notion to the more particular Filipino science fiction, we arrive at the hopefully more satisfactory criteria:
4) science fiction stories that express some fundamental truth about Filipinos
But what fundamental truth, exactly? And more importantly, how do you marry its expression with some strange but plausible conjecture? This is what makes good Filipino science fiction particularly difficult to write -- it requires both an intimate understanding of one's culture, as well as wild and playful leap of the imagination. Then again, that's the case with all good science fiction.
Update: I've changed criteria 2 from
science fiction stories set in the Philippines;
science fiction stories written in Filipino;
because setting is far too close to character (criteria 3). I've also removed some lines to correct an inadvertent tautology pertaining to the central argument.