I guess all Sasuke is there for is to appeal to those girls that enjoy the "hottie" as they call him. Because personally I think the story could've or still could go on without sasuke in it, I mean Itachi would die anyway by someone else's hand (e.g. Naruto and kakashi). The only time I liked Sasuke is in the begining of the manga (don't know if it is the same for anime) is when he gets caught off guard by Naruto with his shadow clone jutsu and literaly puts him in his place
Later when Sasuke manages to get out of Narutos bindings he tells Sakura "you should be more kind to Naruto" or something like that, since he acknowledges how good Naruto has become.