Today, the trend seems to be to base movies on well known comic book characters. Has it ever worked the other way? If so, which Sci-Fi movie character was the first Sci-Fi comic book character to have appeared on the silver screen before it was featured in its own successful comic book series?
I'd like to throw good ol' Mickey Mouse into the mix. Having his movie debut back in 1928 and his comic book series starting in various places around 1937. Donald Duck seemed to be a more popular comic character and even made it into news paper comic strips around the same time, although his animated appearance was far later than Mickey, around 1934.
If Mickey doesn't count as a popular enough comic book character, certainly Donald Duck, who had roughly the same comic book debut, is one of the most popular comic book characters of all time (just ask Italy and Germany).
I've got an earlier one. Gertie the Dinosaur, one of the very first cartoons EVER. Well… During he was making the film, Winsor McCay worked also on a comic serie, Little Nemo in Slumberland. And his upcoming character appeared on September 21, 1913 as a background character in an episode of Little Nemo in Slumberland. Of course, you could argue that it's more a cameo or a nod of the author than really an adaptation, but still, one of the earliest connections.
Also, according to Wikipedia, Winsor McCay's son Robert tried to revive the character of Gertie in comics, during the 1950's, but I don't know if it counts (the original movie was one of the firsts, but between the movie and the comic adaptation, other movies were adapted in other comics… quite debatable).
The earliest example I can think of is James Bond, who jumped from book to movie in 1962 and then from movie to comic series decades later.