The Arclight Cinemas in Sherman Oaks has a lobby display commemorating Hollywood’s comicbook summer. Yet as this year’s onslaught of adaptations marches on, a sobering possibility is emerging that might temper enchantment with caped crusaders.Remember “Iron Man?” With the benefit of hindsight, that might very well have been a fluke. It was “Iron Man,” after all, that made the prospect of mining the Marvel and DC archives so attractive, emboldening execs to believe glittering returns weren’t necessarily confined to the highest-profile superheroes — that is, Batman, Superman and Spider-Man. Now, however, after the arrival of “Green Lantern,” “X-Men: First Class” and “Thor” — which fared a bit better among ticket-buying mortals — the challenges inherent in bringing the comic-book universe’s second-tier characters to cinematic life appear more formidable, and eliciting raucous enthusiasm at Comic-Con offers less reassurance. Lessons from this summer have implications for comicbook fans and studios that have anticipated taking their money while expanding the reach of these properties to meet the boxoffice requirements of summer tentpoles — traditionally a relationship characterized by distrust, and perhaps contempt. Having chafed at camp renditions of beloved characters, comic fans long argued fidelity to and respect for the source material would cure all ills. Then along comes something like “Green Lantern” — and before that, “Watchmen” and “Fantastic Four” — that’s largely faithful to the comics and still manages to prove dramatically inert. Indeed, “Green Lantern” could almost be a case study for how the creative equation surrounding comicbook movies has turned on its head. Those familiar with the comics long saw potential in “Green Lantern,” but feared the intergalactic action elements couldn’t be effectively realized. Advances in computer-generated imagery, however, have made all that feasible. Instead, the movie stumbles in its storytelling and structure, which includes devoting ample time to laying the groundwork for a sequel that possibly won’t ever happen. And that’s despite the involvement of Geoff Johns, the chief creative officer for DC Entertainment, who forged his comicbook rep in part by writing none other than Green Lantern. Then again, even a first-rate film such as “X-Men: First Class” can fail to reach much beyond committed nerds due in part to its immersion in the franchise’s mythology, just as the otherwise enjoyable “Thor” tripped up a bit by deciding to incorporate the title character’s Asgardian pals the Warriors Three. At this point, it looks like these lesser-known heroes can reliably yield solid opening weekends thanks to core loyalists, followed by a precipitous decline. That leaves Disney and Warner Bros. — the proud owners of Marvel and DC, respectively — sitting on a vault of characters who pose a risk in greenlighting a $150-million live-action feature, as Universal learned twice over with stabs at the Hulk that, alas, didn’t smash. Granted, it’s partially the outsized expectations associated with theatrical blockbusters that are leaving these decades-old characters looking a trifle deflated, if not wholly defeated. The logical response, then, would be to mitigate the investment — either via animated (where comics traditionally translate best creatively) or live-action series. Still, NBC’s decision to pass on “Wonder Woman” betrays lurking pitfalls there as well, even though the idea of taking a mediocre comic book — essentially Superman in drag — and trying to make something out of it represented a shrewd gamble. Of course, theatrical rights to Marvel’s properties are scattered around, while director Christopher Nolan has become the de facto gatekeeper of the DC universe by virtue of controlling its two most marketable characters, Batman and now as the producer of Superman. A few more ostentatious setbacks could cause studios to seriously reconsider this trend, just as some are taking hard looks at their Comic-Con commitments, mindful of the “false positive” promotional efforts can register there. As a side note, it’s clear many cinephiles are eager to see the comic-book invasion repelled. In elite critical circles, the tone has been especially dismissive. Paramount’s upcoming release of “Captain America: First Avenger” could still save the day, but barring a redemptive post-Fourth of July rescue, the takeaway from the Great Comic Book Summer of 2011 could well be a rather harsh dose of reality — namely, despite “Iron Man’s” high-flying act, it’s not so easy transforming comics into green.