In the later 1970s, Gulacy took on occasional other assignments, including the covers of the science fiction film adaptation Logan's Run #6 and of the Western The Rawhide Kid #147 , both for Marvel;[6] and a 10-page preview of the graphic novel Sabre: Slow Fade of an Endangered Species, with writer Don McGregor, in the comics-magazine Heavy Metal vol. 2, #2. As a Graphic-novel pioneer he helped create Sabre (1978), one of the first graphic novels. Cover art by Paul With writer Don McGregor, Gulacy created one of the first modern graphic novels,Eclipse Books' Sabre: Slow Fade of an Endangered Species. Published in August 1978 — two months before Will Eisner's more famous, graphic short-story collection A Contract with God — it was the first graphic novel to be sold in the new "direct market" of comic-book stores. Described on the credits page as a "comic novel" (the term "graphic novel" not being in common usage at the time), the trade paperback was priced at a then-considerable $6.00. It helped prove the new format's viability by going into a February 1979 second printing. Eclipse would publish a 10th-anniversary edition with a new Gulacy cover. A 20th-anniversary edition was published by Image Comics in 1998, and a 30th anniversary edition by Desperado Publishing in 2009.

In 1979 and 1980, Gulacy drew several horror/sci-fi/fantasy stories for Warren Publishing's black-and-white comics magazines Eerie, Vampirella, and Warren Presents; some were reprinted in Eclipse Comics Nightmares #1-2 in 1985. Gulacy also drew the cover and the six-page story "Libido", written by his Master of Kung Fu colleague Doug Moench, in the comics magazine Epic Illustrated #3 . Along with the covers for independent publisher Capital Comics' superhero title Nexus #1-2 (, Gulacy drew covers and an occasional story for such anthology series as Marvel's Marvel Preview and Bizarre Adventures and Eclipse Comics' Eclipse: The Magazine. In 1983, he drew several covers for independent AC Comics' Black Diamond, Americomics, Starmasters, and Femforce Special before reteaming with Moench on the four-issue, creator-owned Epic Comics miniseries Six from Sirius Through the remainder of the decade, he drew primarily for Eclipse (and Dark Horse Comics. Gulacy also began working for DC Comics with Batman #393-394 , and the six-issue miniseries Slash Maraud , co-created with Moench. The two also collaborated on a series of eight-page chapters starring the superhero Coldblood which ran in the biweekly omnibus Marvel Comics Presents #26-25. During the 1990s, Gulacy worked primarily on Batman and such science-fiction movie properties as Terminator, Predator, and Star Wars, and co-created the Valiant Comics crime series Grackle.

Among the many titles Gulacy has drawn are the DC Comics Batman, Batman: Legends of the Dark Knight ("Batman: Prey"), Batman: Outlaws, Year One: Batman/Ra's al Ghul,[11] Catwoman, Green Lantern: Dragon Lord and JSA: Classified; Acclaim Comics' Eternal Warrior and Turok, Dinosaur Hunter; Dark Horse Comics' Star Wars: Crimson Empire; and Penthouse Comix's Omni Comix. In 2002, he combined his interest in science-fiction and spy stories in DC Comics' S.C.I. Spy, and that same year returned to his signature character with his and Doug Moench's six-issue Marvel miniseries Shang-Chi: Master of Kung Fu. Other Marvel work includes collaborations with writer Marc Guggenheim on the four-issue miniseries Squadron Supreme: Hyperion vs. Nighthawk and with writer Cary Bates on True Believers.

In 1982, Rubinstein inked the acclaimed Wolverine limited series. One of his most important works has been inking The Official Handbook of the Marvel Universe over a span of twenty years, for which he holds a Guinness World Record of inking more pencilers than any other inker. Rubinstein recounted, I did an inker's round table for a magazine called Comics Scene, where Klaus Janson, Tom Palmer, Bob Layton and myself all inked a Mike Zeck drawing. Mark Gruenwald saw these and decided that mine was the clearest to understand what the character looked like, not necessarily the best inked, and when I came back from the San Diego con ... Mark said, "We're doing this encyclopedia, and we would like you to ink as many of the figures as you want." And I said, "I'll ink all of them," which turned into a gold mine and a godsend.  And he picked me because he knew that I would not make a homogenous look of it, and I honestly think I chameleon my style enough..

Among his extensive inking credits (which include more than 2,500 comic books), were work with Michael Golden on Micronauts, Jim Starlin's Warlock and Aquaman with Don Newton. Later assignments included a mini-series for Dark Horse Comics called Archenemies, and co-inked issues of DC Comics's Ion mini-series and Green Arrow/Black Canary.