McMurphy: Part of the problem with people citing Aldiss may be because he does expend an enormous amount of space in that book on this claim. Not only in the initial chapter where he brings it up (a rather lengthy chapter that spends considerable time on this particular novel), but it is heavily peppered throughout the work -- and
Trillion Year Spree is a rather large book!
As for the claims for Mrs. Shelley, I hope I made it fairly clear that, while I consider her an enormous influence and progenitor of the field, I don't think she belongs as a science fiction writer in our current view of the field. Hers was the bridge between the then-fashionable Gothic tale, the sentimental novel, and the emerging scientific romance. If I did not make that position clear, then I apologize.
AW: as for your new list:
H.G. Wells -- I don't think anyone would deny Wells a high place on any list of sf. He's got more well-known classics in the field than you can shake a stick at -- and well-known enough for most people on the street to be aware of him at least from film adaptations of various works
H.P. Lovecraft -- As I believe I said earlier,though I am a very big fan of HPL, I don't believe he belongs on the list, save tangentially. His intent was never to write science fiction (or scientifiction, or "interplanetary fiction", that last being his own term for it) at all. He may have been taken into the field in retrospect because his work (at least his later work, what he called "a non-supernatural form of cosmic art") is based on a mechanistic view of the universe; but I think any claims for his stories as sf are, while not without some merit, rather tenuous.
Isaac Asimov -- Here we run into problems. Asimov is well-known because of the breadth of his topics, more specifically for his sf, if using the criterion you noted above of it being "mainstream" in the sense of the mass of people (rather than "the mainstream within the genre"). Yet there is no argument that he remains one of the most visible and highly respected figures in the field, and has numerous novels and story collections which are considered classics, from
I, Robot and "Nightfall" on.
Jules Verne -- in the same class as Wells, I think. Still read regularly, well-known both from his books and film/tv adaptations of his work, and read far beyond the limits of sf fandom (or even casual readers of sf); and has numerous classics in the genre.
Mary Shelley -- I think I've addressed this one numerous times above. But, if we're going to include her as a genuine writer in the field, rather than one of those whose work was highly influential on but doesn't quite belong (as with such writers as H. Rider Haggard, I'd say; another enormously popular writer, many of whose works are still in print over a century after they were first published, and who has had several film adaptations of at least a handfull of them), then the claim would be not only for Frankenstein but The Last Man and several of her shorter tales (both short stories and novellas such as "The Mortal Immortal").
John Wyndham -- I'm not sure he belongs with "mainstream" here, as most people have probably never heard the name, though they've seen the films of
Children of the Damned (
The Midwich Cuckoos) or
Day of the Triffids. But, again, someone who has numerous classics in the field, including
The Chrysalids,
The Kraken Wakes, etc.
Philip K. Dick -- Dick definitely belongs on there. He's now had numerous film adaptations, his works are more popular than ever, and he is one of the few writers in the field to write classic novels exploring the themes of epistemology and ontology. Even if only for
Do Androids Dream of Electric Sheep, he is popularly known enough now to merit being on there.
Arthur C. Clarke -- Clarke's name is familiar not only due to the series of books beginning with 2001 and the movie of that title, but also because he's hosted Arthur C. Clarke's Mysterious World, as well as being cited as one of the creators of the telecommunications satellite.
Now... as for those you've forgotten:
Frank Herbert has already been named. Dune, which is extremely well-known, and, as of God-Emperor of Dune, the series has remained best-sellers in the mainstream as well as sf community.
Robert A. Heinlein -- A well-known figure both in and out of sf (a lot of his material was published in mainstream magazines such as Saturday Evening Post, has numerous classics of the field ... well, let's face it, the better portion of Heinlein's work has been considered classic (as well as controversial) in the sf community since the 1940s; and
Stranger in a Strange Land,
The Number of the Beast,
Friday,
Job: A Comedy of Justice,
The Cat Who Walks Through Walls,
To Sail Beyond the Sunset, and others have all been best-sellers; his juvenile series have remained in print since they began back in the early 1940s, he invented what became
Space Cadet on television... Should
definitely be on the list.
Rod Serling -- Not only for his creation of (and writing scripts -- and later prose story versions of stories from)
The Twilight Zone, which certainly fits in the average person's definition of sf, but because he also co-wrote the screenplay for
Planet of the Apes; and he's rather well-known outside the sf community as well.
Richard Matheson -- His novels are well-known outside the sf community, he's had numerous film adaptations of his books (many of which he wrote the scripts for, as well as doing film adaptations of other works, and numerous scripts for television); his novels include
I Am Legend and
The Shrinking Man.
Those are a few I think I'd put on the list...