LIKE our choices for best film actresses last Saturday, today's list of the best Filipino film actors of the 20th century honors, not particular or occasional performances, but the overall significance of outstanding actors' career-long work. Relevant here are versatility and a consistently high level of achievement.

Again, innate acting talent has turned out not to be enough to lead to cumulative excellence in film performance. We have some very gifted actors who are relegated to relatively unchallenging roles that don't showcase their talent as it deserves to be highlighted, more's the pity.

Key factors here are the support of a major studio and having an excellent director as mentor. Some actors who may not be great performers to begin with, if properly honed and given a series of challenging roles that draw out the best in them, are able to scale unexpected thespic heights.

This is not to say that they are mere products of a mechanical process and thus undeserving of admiration, because the same ''system'' has been applied to other actors but they didn't come into their own, despite all the help and showcasing they had been given.

Clearly, great acting in this country is the result of a confluence of factors, of which the actor's own sensitivity and desire to do his very best are not the least consequential. When we honor actors, therefore, we honor not their discoverers or their studios, but their excellent performances themselves. In the final analysis, what's important is their series of superior portrayals, no matter how they were devised.

Our best-actor honorees (in alphabetical order):

ROGELIO DE LA ROSA

One of local movies' most popular matinee idols, he also acted well in a number of important movies like ''Higit sa Lahat,'' ''Bituing Marikit,'' ''Sa Paanan ng Bundok,'' ''Florante at Laura'' and ''Garrison 13.'' It was ''Higit sa Lahat'' that gave De la Rosa his highest acting honor-the best actor trophy at the 1956 Asian Film Festival.

CHRISTOPHER DE LEON

A good example of the raw talent honed by an excellent director (Lino Brocka), Christopher came out from anonymity to play the young male lead role in ''Tinimbang Ka Ngunit Kulang,'' for which he won Famas' Best Actor plum in 1976.

He didn't remain an exclusive Brocka talent, however. He also made outstanding films with the similarly excellent likes of Ishmael Bernal (''Broken Marriage,'' ''Relasyon''), Mike de Leon (''Kung Mangarap Ka't Magising'') and Eddie Romero (''Ganito Kami Noon, Paano Kayo Ngayon?'').

DINDO FERNANDO

The outstanding dramatic actor first came on strong in edgy films like ''Psycho Maniac,'' but grew less hyper in movies like ''Binhi,'' ''Ikaw at ang Gabi,'' ''Inay'' and ''Muling Buksan ang Puso.''

Although he was generally limited to highly dramatic roles, Dindo could also turn wickedly playful, portraying offbeat characters in satires on contemporary sexual mores-a tribute to his range and versatility.

JAY ILAGAN

He was the young actor of his generation, but he put on too much weight and thus lost plum roles to the likes of Christopher de Leon and Bembol Roco. Still, Ilagan was able to notch enough excellent performances in films like ''Santiago,'' ''Tubog sa Ginto,'' ''Brutal,'' ''Sister Stella L,'' ''Soltero'' and ''Kisapmata'' to make it to our list.

His performances were distinguished by sensitivity, versatility and a natural, even seemingly offhand approach that hinted at more troubling developments yet to unfold.

PANCHO MAGALONA

Regarded by some as ''just'' a song-and-dance man and romantic-comedy lead, Pancho has in fact come up with complex characterizations in ''El Filibusterismo,'' ''Cry Freedom,'' ''Hanggang sa Dulo ng Daigdig,'' ''Pipo'' and in an American war film in which he played a Korean prisoner of war. And his romantic-comedy films, many of them with Nida Blanca, required a combination of skills that few of his contemporaries possessed.

JOSE PADILLA JR.

A leading light of Philippine show biz's illustrious family, Padilla began his acting career in 1931 in the silent film, ''La Monjita,'' and went on to craft strong performances in ''Magpakailanman,'' ''Sanda Wong'' (where he was last cast in the title role) and ''Sawa sa Lumang Simboryo,'' where he played a bandit leader.

BEMBOL ROCO

A Brocka discovery like Christopher de Leon, Roco first acted in an episode in ''Tatlo, Dalawa, Isa'' but came into his own as the lead actor in ''Maynila, sa mga Kuko ng Liwanang,'' where he portrayed the empathetic, tragic role of Julio Madiaga. His other memorable performances have been in ''Sakada,'' ''Sa Piling ng mga Sugapa,'' ''Tatlong Taong Walang Diyos,'' ''Gumapang Ka sa Lusak'' and ''Orapronobis.''

RUBEN RUSTIA

Rustia played lead roles in films like ''Haring Tulisan,'' but it's as a character actor of rare versatility, depth and creativity that he has made his indellible mark on Philippine films, eliciting the admiration of his peers.

His more memorable performances have been in films like ''Sisa,'' ''Pedro Penduko,'' ''King and Emperor,'' ''Banta ng Kahapon,'' ''Kisapmata,'' ''Noli me Tangere,'' ''Stardoom,'' ''Nunal sa Tubig'' and ''Sister Stella L.''

LEOPOLDO SALCEDO

Billed as local movies' Great Profile, Salcedo eventually proved that he had more than just chiseled good looks going for him. He won a Famas best actor award for ''The Moises Padilla Story'' and a best supporting actor trophy for his performance in ''Ganito Kami Noon, Paano Kayo Ngayon?''

Other films in which he turned in his characteristically textured and assertive performances include ''Sakay,'' ''Ararong Ginto,'' ''Highway 54'' and ''Noli Me Tangere.''

PHILLIP SALVADOR

The Brocka actor who acted in the greatest number of movies for the acclaimed filmmaker, Salvador has these important films to his credit: ''Jaguar,'' ''Bona,'' ''Kapit sa Patalim: Bayan Ko,'' ''Orapronobis'' and ''Rubia Servios.''

As an action star, he also won acting awards for his performances in ''Balweg'' and ''Boy Negro.''

TONY SANTOS SR.

A mature character actor with a non-filmstar, ''everyman'' quality, Santos also played lead roles in film classics like Avellana's ''Badjao'' and ''Anak Dalita'' and Manuel Silos' ''Biyaya ng Lupa'' and ''Batalyon XIII,'' as well as memorable supporting parts in movies like Mike de Leon's ''Sister Stella L.''

VIC SILAYAN

The only actor who figured in all of our resource persons' best-actor citations, Silayan was admired by his colleagues in the acting profession for his ability to combine naturalness with intensity, range and depth.