“Superboy” was the one-word sales pitch when the series that became “Smallville” was birthed, and comicbook aficionados could be forgiven if the title engendered less than complete enthusiasm.

After all, comic characters to that point had a somewhat abusive relationship with cinematic adaptations in general and television in particular. From the “Superman” series in the 1950s to the “Biff! Wham! Pow!” of “Batman” in the ’60s to “The Incredible Hulk,” “Spider-Man” and “Wonder Woman” in the ’70s, comics-based programs had variously indulged in high camp or been characterized by puny special effects that, at best, were highlighted by savaging a tear-away wall.

Even the big-budget “Superman” movie, starring Christopher Reeve — with a section showcasing Smallville’s amber waves of grain that provided the basis for a teenage Superman series — yielded its share of teeth-gnashing among fans, what with its over-the-top villain, Lex Luthor, and his equally absurd sidekicks.

“Smallville,” however, proved a pleasant surprise — a show that paid homage to the Superman mythology while carving out a path of its own, one that boldly reimagined the character’s Kryptonian roots while staying true to the underlying source material. And, go figure, the series managed to accomplish that under the stewardship of Al Gough and Miles Millar, a writing team who confessed to having no special affinity for comics.

At first, of course, there was grumbling about the supervillain-of-the-week formula, with some unlucky teenager morphed into a monster by the meteor rocks, otherwise known as Kryptonite, which showered Kansas along with the arrival of young Clark Kent (Tom Welling).

Soon enough, though, “Smallville” began to take an intriguing shape, what with the tenuous friendship between Clark and his eventual nemesis Lex (Michael Rosenbaum), charting the influences that not only prepared the former for heroics but steered the latter toward evil.

Ditto, in the most pronounced departure, for “Smallville’s” treatment of Superman’s Kryptonian father, Jor-El, who sent him to Earth not to help the planet’s inhabitants but to conquer and rule as he wished. Suddenly, the values ingrained in Clark by his way-cool adopted parents the Kents (John Schneider and “Superman III” alumna Annette O’Toole) seemed even more significant — the ultimate battle of nature vs. nurture.

Balancing the loving foundation provided by the Kents is the inevitable road to the dark side traveled by Lex, whose relationship with his father (John Glover) and gradually fraying friendship with Clark provide the show’s most intriguing dynamic.

(It’s worth noting that the “Superboy” comics also featured a young Lex, though the explanation for his descent into villainy — an accident that caused him to lose his hair — is one probably best forgotten even by comicbook fans.)

Still, fealty to the spirit of the comics alone would hardly explain “Smallville’s” resilience, surviving a handful of time-period shifts, including the always dicey proposition of being relocated in its fifth season, when viewer loyalty is easily shaken. Part of the show’s durability stems from its playing on multiple levels to different constituencies. At various moments, “Smallville” is an action hour, sci-fi romp, teen soap, family drama and rethinking of comicbook mythology — often all within the same episode. Small wonder that when the program was honored by the Museum of TV & Radio, the audience included children, teenage girls swooning over Welling and middle-aged men, asking about Clark’s wardrobe and where the TV show exists vis-a-vis the films.

These elements are very much in evidence within “Smallville’s” impressive 100th episode, which airs tonight and brings the series to something of a crossroads. Clark, after all, is no longer a high school lad but a young man, with the now-28-year-old Welling’s presence already requiring some suspension of disbelief.

All good things must come to an end, and this series is certainly no exception, whether it’s next season (where it may be moved over to the new CW net) or the year after. Indeed, the WB’s shortcomings and the WBTV-produced program’s relative success probably have conspired to keep it alive longer than is logistically prudent.

Superheroes have become ripe fodder for splashy theatrical incarnations thanks to the blessings of computer graphics, but it shouldn’t be overlooked that “Smallville” was part of that revolution — blazing its own big red “$” sign across the small screen, and helping to do penance for the sins of TV series past.