When Chuck first came out, a friend of mine had a theory that NBC executives were trying to duplicate the success of resident heartthrob Jim Halpert (John Krasinski) by casting a look alike, give him the same haircut and nebbish good boy manners. That may be so, but Chuck is no second rate Jim Halpert, and Zachary Levi is a much better actor and way hotter. Can you tell that I kinda dislike John Krasinski? I don't know, to me he has the hacky fake good guy vibe of Zach Braff, and about as much acting talent.
I actually recognized Zachary Levi from the little known sitcom Less Than Perfect, where he played a very different character, a super metrosexual cutthroat up and comer who was lovably shallow. I was pretty impressed by his range, and he continues to be super adorable and funny on Chuck. Also unlike John Krasinski, I don't see him telegraphing Chuck's kind hearted manners. And for that, he is the Hot Guy Of The Day.