I think on the underrate - overrated list Big Show is just in the middle, he is in a pretty decent position, he doesn't need to be there to carry the world championships, he can do it, but it's not something he needs to do for him to go great, he's more of the upper mid-card guy who can carry both the mid-card and the main event.
On the list of things in the poll I would say that The Big Show is great, he has a great character that works very well with both his face side and his heel side, right now he's doing great as a face, he's entertaining, and he has great microphone work, something that shined through during his time with his feud with Jack Swagger.
The heel part of him is also great, because of his size and because of his dominating look he can easily play a heel in terms of looking terrifying and the dominator in terms of pushing around the faces in the ring, and making them look great when they beat him.
His side comes into advantage for him because he becomes the dominant guy that can EASILY put people over if they manage to dominate him, something a regular guy like Chris Jericho and Shawn Michaels couldn't do, they had to have great matches to properly put someone over as opposed to a big guy being dominated which makes the opponent look strong.
About the world title reign, I'd say sure, I wouldn't say that I would have a problem giving the belt to Big Show, because he's a great act as a face right now, and definitely could run with the belt on Smackdown, but I also say he does not need to have a reign for me to enjoy him.