Ah, Subby....let's see...(brace yourself - history lesson with editorial comments to follow)
The Timely/Atlas run of "Sub-Mariner Comics" began in 1941, with so-so sales. Title changed to "True Crime Comics" with issue #24, and "Amazing Mysteries" with issue #32 in 1949, which ended the initial run. It brought back five years later with issue #33 for short run of less than two years, ending with issue #55. Several of these older talkes have been repirinted. They are okay, but nothing to write home about. Sort of an Aquaman-wannabe.
The character was brought back in 1962 by Stan Lee in the now classic Fantastic Four #4. Showed up in the FF's book a couple of times each year, with cross-overs in other Marvel books as well, until Tales to Astonish #70 in 1965, where Subby was half the book (the Hulk being the other half). These issues were THE BEST SUBBY STORIES EVER! Gene Colan's art was fantastic, and the character took on a regal fantasy-kingdom setting. The half-issue story length helped rather than hurt.
Then in 1968 they screwed it up by giving both Hulk and Subby their own books. Gene Colan left, and the book fell into mediocrity, with very forgetable stories. Then with issue #50 it was resurrected when original Subby creator Bill Everett came onto the book. It took on a nostalgic 1940's feel to it, which was a sharp contrast to the other Marvel books of the 70's. Everett died while penning issue #61, and nobody was able to do anything with the book after that. They even attempted to give him a new costume, which was awful, and the book itself died with issue #72 in 1974.
A year later Marvel launched "Super-Villain Team-up" staring Doctor Doom and the Sub-Mariner, which thankfully only lasted for 17 issues. One main problem with this book is the fact that for the previous decade Subby had been presented as a hero rather than villain. In fact, he was a hero in the simultaneous-running WWII "Invaders" book. Marvel eventually recognized that fact, dropping Subby from the title and teaming Doc Doom up with real villains like Magneto and the Red Scull, but by then the book was already dead. In 1990 John Byrne decided to take his crack at this misunderstood character, with the launch of "Namor". Byrne stuck around for a couple of years and took a whole new take on the character, actually making him interesting. After he left Jea Lee came onboard, and the book took a preachy "Environmentalist" tone to it. The book eventually died with issue #62 in 1995.
In the eight years since then he has made cameo appearances and had a short mini-series. He's been a part of several teams, The Defenders being the main one, although he has also joined both the Fantastic Four and Avengers for short, forgetable runs.
Of course the main advantage to bringing this Grade B character to the silver screen is that they can make some radical changes and not get everyone into a uproar. Think Blade, who was a Grade C Marvel character, and is now getting a third film. I think the Rock is a great casting choice, better than Nick Cage who was originally being considered for the part.