It's never confirmed that Sheldon is the smartest of them. You only have his words for that. He's always working on sth big, but never delivers. And there are dozens of other smart people and geeks in the show, most of them likeable. I don't have a problem with show full of geeks, in which one of them is asshole. Seems fair.
I do think that's actually a hole in the show. One can infer socially that Sheldon really must be all that or he'd be long-since fired, but it would be helpful to be a bit more direct in occasionally showing it.
I've also noticed that for all they dump on Howard, he's the only one in the show who they show accomplishing things (plural!); I have not yet figured out if this is dramatic oversight or something they are doing on purpose. I'm assuming accident; neutering your main characters like that isn't a good narrative move, unless they're being really meta (which I doubt in this case).
