Perhaps there's a reason the Elongated Man never made it into the top tier. Too hard to spell. Difficult to pronounce. Doesn't clearly say what his power is. Difficult to work the word into a dynamic logo.
Well, perhaps there are several reasons.
It is difficult to come up with a name that hasn't been used. The Elongated Man dates from 1960, but editor Julius Schwartz has said that if he'd known that DC owned the rights to Plastic Man at the time, he would have used that name instead. He could have gone with Elastic Man, but Superman's Pal Jimmy Olsen was having intermittent adventures as "Elastic Lad". Worse, Jimmy and EM both wore relatively featureless purple tights--although Jimmy had the worse taste to actually have "Elastic Lad" on his chest.
Even the Incredibles' "ElastiGirl" was already taken. (Uncharacteristically, she was the "muscle" of the Doom Patrol. She didn't stretch, she grew to gigantic size.*) (I remember reading at IMDB that DC allowed Pixar to use the name in the film so long as it wasn't used in merchandising. There are precious few toys of Pixar's ElastiGirl, and the only one I can find, the cloissone pin, is labelled "Mrs Incredible".)
So, actually, the Elongated Man is the only major stretching superhero whose name doesn't rhyme with "plastic".
Most of them are played for laughs, anyway, with the conspicuous exception of Reed Richards, the Fantastic Four's "Mr. Fantastic". (Usually. Remind me to tell you about the time Dr Doom was bragging about having his own European country and Reed shot back, "I have a hundred pairs of stretch socks!"** But it still rhymes with "plastic".) I suppose when you think about the kind of distortion these characters are theoretically capable of, you could go either grotesque, or goofy.
I'm taking this too seriously, I guess.
* By the way, that green kid on the "Doom Patrol" cover? That's Beast Boy. Yeah, the same one who's currently appearing in "Teen Titans."
** Okay, I cheated. The "stretch socks" scene wasn't in any "real" adventure of the Fantastic Four. It was a parody in the pages of Marvel's short-lived but fondly-remembered "Not Brand Ecch." The funniest part of this uneven humor title was just how short the distance was from Stan Lee's melodrama to out-and-out comedy.
More information: Great Comic Book Database (from whence the covers come): Dibny Dirt, the Elongated Man Website.