Jim Starlin was heavily influenced by Jack Kirby, Stan Lee and Steve Ditko. His acclaimed work has made him just as influential to many writers.

He worked as an artist on Iron Man, where he introduced Thanos. The character was an homage to Jack Kirby's Darkseid.

He was given the job to plot Captain Marvel, a poorly selling Marvel space hero. Starlin did wonders for the book, creatively, critically and sales wise. He created an elaborate history and characters for the universe outside of Marvel earth, with characters, themes and ideas still used today by any writer that goes off-planet. Later on he went to do the Adam Warlock series, exploring complex themes such as religion, destiny, death and the meaning of life.

He was given the opportunity to "kill" Captain Marvel after the characters sales declined after he left the book. Crafting an intricate plot that ended with the mighty space hero falling to cancer, The Death of Captain Marvel is an enthralling and endearing saga that still holds up today.

He then worked on Thanos, expanding on his origin and motivations. His work made Thanos a cosmic powerhouse. He wrote The Infinity Gauntlet, Infinity War, and The End of the Marvel Universe starring primarily Thanos.

In 2006 he revamped DC's Captain Comet alongside artist Shane Davis in the Mystery in Space miniseries.