As for the other versions, it looks like the Classics Illustrated comic was issued in 1954 (though I'm not absolutely certain), so it may have come out after the George Pal movie was released. In any case, I'm pretty sure I read the comic after I'd seen the movie. The Martian fighting machines are different. They fly in the movie, but in the comic they're closer to how Wells' described them--moving on three leg-like appendages. These were the inspiration for George Lucas' Imperial Walkers (Lucas was just a couple of years older and also must have seen the 1953 movie at an impressionable age), and Spielberg uses this three leg model for his 2005 movie.
As for the 1938 broadcast, writer Howard Koch (who also wrote the screenplay of Casablanca) wrote a book about it called The Panic Broadcast. It's not entirely reliable--he claims that he used nothing of the Wells story but the premise, but he actually borrowed a lot more, including characters, plot and entire chunks of dialogue. He does say that doing it was Orson Welles' idea (and no, Wells and Welles weren't related) and that Orson suggested doing it as a series of news bulletins, which is what really gave it its power.
The 1953 movie--which I have on DVD and still love to watch--was based as much on the Mercury Theatre version as on Wells' novel. It also transferred the story to the U.S. and updated it to contemporary times. In Wells' time, people were fearful of the approaching Great War; in Welles' it was the approach of World War II. This film is very much a Cold War fear film: fear of the unknown Soviets, of nuclear bombs and advanced science, etc. which fueled a lot of 50s sf and Bug-Eyed Monster movies.
In the novel, the Martian invasion is mostly seen through the eyes of an ordinary (if educated) person. The radio play told the story through interviews of major figures: military leaders, political leaders, scientists. That pattern is followed in the Pal film, but there are two characters the audience identifies with: a young scientist and the young woman he falls in love with during the invasion.
The 2005 Speilberg movie returns the point of view to an ordinary person--there are no real authority figures in the film. But at the same time, the scientific curiosity of the novel's protagonist is gone. What we have is Tom Cruise as an errant father learning to assume responsibility as he and his children flee from the invaders.
When I saw the Speilberg film, something in particular interested me: as a child, I still identified with the scientist in the Pal film. I watched how he treated the young woman, and I rooted for him to come up with the scientific solution. In fact, one of the scariest scenes in the movie still is the moment when panicked humans--not the Martians--destroy the scientists' equipment and injure several of them, ending their attempt to find a solution. But even though there are children in the Spielberg film, I wonder who children seeing it would identify with. The kids? Tom Cruise? Neither seems very appealing to me.
Of course, Speilberg did dazzling effects, but the effects in the Pal movie were pretty amazing for their time, and if you don't look too closely at the DVD, most of them still work. This is especially impressive because alot of what they did were true special effects--that is, effects done live, not the "visual effects" created later, these days by computer. There was model work (the miniatures of Los Angeles buildings were very detailed) etc. but the models of the Martian ships had a lot of electronics and working parts.
Beyond the scope of the effects, there just seemed to be a lot more at stake in the Pal version--especially in the 50s, when such a movie could just as well end with the end of the world as with a happy resolution.
One other thing about the Pal movie. It begins with the narrator describing the Martians on their dying planet, looking to nearby worlds for a new home. All the planets in the solar system are considered before they settle on Earth--except Venus. This might be because in Wells novel, when the invasion of Earth fails, the Martians colonize Venus, and are no longer a threat to Earth.
I've written a lot more about the various versions of The War of the Worlds, including an unacknowledged remake called Independence Day, here at Soul of Star Trek.