Yeah, I think if you watch the first few episodes of Supernatural, you can see that Jared had a similar kind of look to Clark, in that he was this young guy who was a little scared because of the life he had, and just wanted to be normal and fit in. In some way, you can almost make the argument that the relationship between Sam and his dad was very similar to the relationship between Clark and Jor-El.
Jensen's a great actor, but in the roles I've seen him in during his time on Smallville and Supernatural, I just don't get that same vibe from him, even though the roles he played are completely different than Clark. Ironically though, Eric Johnson, who went on to play Whitney, was the favorite before they found Welling. Imagine how that could've went.