When approaching Gary Westfahl's online SF resource, the key thing to remember is that it's described as a work in progress. This is the only thing excusing the absence of an entry for Georges Melies, who arguably invented the SF film to begin with. With that in mind, let us proceed.

Westfahl's avowed inspiration for his own text is David Thomson's Biographical Dictionary of Film, both in its insistence that while film-making is collaborative in nature, it remains the work of identifiable individual talents, and in its insistence that the author's opinions about his subject should be stated boldly and clearly. Westfahl inarguably meets the latter of those conditions immediately, saying of Thomson himself:

regardless of his other virtues, Thomson happens to be consistently wrongheaded on those rare occasions when he considers science fiction films (I mean, the man prefers Metropolis to 2001: A Space Odyssey, for heaven's sake.)

Regrettably Westfahl has entries for neither Fritz Lang nor Stanley Kubrick to demonstrate exactly why this is so wrongheaded of Thomson. I like both Metropolis and 2001, though I do prefer the latter to the former. Then again, I like 2001 better than many other films too. Anyway.

Westfahl seems to have gone online with his text primarily for the simple reason that he seems to have been unable to obtain a print publisher. Curious, since as he notes his book is pretty much unique, and you'd expect a publisher would be keen to pick up a book like that (odder still when you see how specialised some SF reference books can be). Still, the online format has its uses. Primarily it allows the liberty of adding to the text incrementally, and Westfahl promises to add a couple of entries per month. (I estimate, therefore, that he should be finished circa 2014 at his present rate, since he claims to have drawn up credits for 400 individuals before starting and currently has nearly ninety complete entries. That's assuming he doesn't add any more over the next decade, either, else he might never finish.)

The incomplete text that exists, then, is a strangely haphazard one. A number of key figures are missing (we might also wonder at the absence of Leonard Nimoy when his Star Trek compatriots William Shatner and George Takei are here), while a number of personages that could be called peripheral at best are present (The Beatles, Ben Hecht and Anthony Quinn, anyone?). Would it not have made more sense to start with the more commonly recognised "important" figures and add the secondary ones later? Why does a non-entity like Frederic Gadette merit being written about before Fritz Lang does?

Unfortunately, too, the reader may feel (as I do) that Westfahl's negative judgements stand out in the memory more than his positive ones. Examples:

Nick Adams: "...once you link together the phrases 'handsome young actor,' 'absolutely no talent,' and 'briefly famous,' it is almost inevitable that 'recurring star of bad science fiction movies' will be added to the string."
Gerry Anderson: "If the nations of the world ever decide to stage Nurenberg Trials to punish the makers of bad science fiction film, Gerry Anderson will be the first defendant."
Tim Burton: "Sorry, you're not paying me enough money to figure out Tim Burton."
John Carradine: "...he displayed no real appreciation for the genuinely unknown or genuinely unearthly; rather, he tried to convey the strange and terrifying only with a tired repertoire of acting tricks."
Lon Chaney Jr.: "Lon Chaney, Jr. never gave a good performance in a horror or science fiction film. With his extremely limited talents, the only roles he could really play were ordinary people--as in the westerns that he came to prefer--or less than ordinary people--like Lenny in Of Mice and Men (1939), his only competent portrayal."
Louise Fletcher: "...she is at her best only when she is playing a bad actress."
Lorne Greene: "...acting in science fiction films generally demands a modicum of intelligence, and if that intelligence wasn't in the script, Greene couldn't, or wouldn't, provide it."
Nathan Juran: "...if you're planning a revival-house double feature to punish your worst enemy, you should seriously consider Attack of the Fifty-Foot Woman and The Brain from Planet Arous."
Glen A. Larson: "...no business other than the entertainment industry would ever be so irrational as to allow a proven incompetent like Glen A. Larson to keep churning out his trademark mistakes."
Christopher Lee: "...always acts in an utterly joyless manner, displaying absolutely no pleasure or interest in what he is doing."
George Pal: "...when it came to science fiction film, George Pal just didn't get it."
Keanu Reeves: "...one of those rare performers who keeps getting worse and worse as his career progresses."
Roy Scheider: "No one told Scheider that understatement is one key to successful film acting."
Steven Spielberg: "...an insufferably awful director and a pernicious influence on the entire genre."
George Takei: "George Takei is such a nice man--so unfailingly friendly and accessible to Star Trek fans, so consistently supportive of Asian-American performers and causes--that it really is such a shame to report that he is such an awful actor, probably the least talented regular in any of the Star Trek series."
Peter Ustinov: "Accounts of Sir Peter Ustinov's life always emphasize how many different roles he has played... They are too kind to point out that he didn't do any of these things particularly well."
Edward D. Wood Jr.: "Someday, western civilization may mature to the stage where people realize that it is not polite to stare intently or giggle at crippled movies."