It seems to me there are two categories of people – when you boil it down.
Those telling what they think is the truth.
Those telling what they know is a lie.
Was Buddha a liar? It doesn’t seem like he would be, because he seems to attribute his ideas to himself, or at least to a process. He then says give it a go yourself. Seems simple enough. Yes, this makes the big fat assumption that said ideas where from Buddha, and, as SAM’s post points out, they very well may not be. But the point is, he doesn't legitmize his ideas with some bullshit they came from a God. He's a Philosopher.
Was Jesus a liar? Well now, lets make the assumption there was a Jesus (something I personally don’t think is true, but for arguments sake). I’d say maybe. Or maybe crazy. Or, more than likely, some other people made it all up, along with Jesus.
Was Mohammad a liar? Again, I’m not convinced he even lived. But, if so, it seems the evidence suggests either yes or crazy. I’m not sure which way to go, people say he was a smart man, if so (and he was not crazy) then he was obviously a liar. The stories are based on Xian stories, the chances of coming up with the same tales out of the blue is zero. There is a chance he was crazy. He did have “fits”. If he had heard the stories and then he heard some voices in his head, well, maybe these voices retold the stories and he thought they were an angel. More than likely some other people made most of it up well after the fact. That's the way this stuff usually goes.
Was Joseph Smith a liar? I’d say the evidence is saying hell yes. Dumb, dumb dumb dumb, DUMB. There's a chance he was crazy. But I really think he was a con artist.
Was Ron a liar? I’m leaning yes. At least he had the presence of mind not to be a plagiarist as well. I suppose as an author he could at least appreciate that much. That said, I thought Ron started Scientology from Dianetics? He DID found a religion didn’t he? There’s also a chance he could be crazy. I'm betting con artist and liar.
Was Claude Vorilhon (founder of The Raëlian Movement) a con? You know, I think he really believes that aliens abducted him. I would think theists would like to learn about him. I mean, he’s a Living Prophet. Maybe they can glimpse a little of what their religion’s founder was like. At least the psychological aspects could be intriguing.
Then there’s Asguard’s point that religion was used to control people. You know, of course it was, BUT, I think way WAY back in the day. Say in the time of the Pharaohs, their writings seem to suggest that everyone was plugged into thinking about Gods for all aspects of life. They really believed they were connected to the Gods. All evidence suggests they were not liars. We’d actually have to go back in time, to a time when we were pre-Homosapien primates and just when our culture was developing. At this time, the belief in Gods gave us an edge (we’re starting to unlock the proteins that control this – studies are now showing even being “conservative” is genetic). Anyway, I’d say at THAT point in our evolution we believed it. Oh probably people lied now and again, but more than likely they believed. The balance between the two could be an intriging study.