Despite his myriad of physical skills, the reality of Oliver's mortality has never been absent from Arrow. Near-death experiences are far from uncommon, and the twisted array of scars that he's accumulated is proof enough that he is not invincible. The conflict inherent in his attempts to regain his humanity by saving his city with minimal bloodshed while facing nemeses unafraid of fighting dirty has been paramount to his journey as a hero. Villainy works differently in Central City. Death is far less prevalent, and facing metahumans has enabled Team Flash to generally win the day by discovering a weakness in the villains' abilities that will allow Barry to subdue them with his superspeed rather than resorting to lethal force. The same could not be said of Oliver Queen as the Arrow. Oliver would have died a dozen times over as the hero of The Flash; when the shows inevitably start sharing characters on a more regular basis, Oliver may not be able to fare well - or with any dignity - against a Flash villain imported to his own show.
Fiction buff and writer. If it's on Netflix, it's probably in my queue. I've bought DVDs for the special features and usually claim that the book is better than the movie or show (and can provide examples). I've never met a TV show that I won't marathon. Follow on Twitter @lah9891 .