When Itachi used susanoo he already had the MS activated, its susanoo that activates instantly. We have seen many times that activating MS cud take 3-5 secs, and for some ppl much longer as seen with Itachi and Kakashi. Now, a kunai can come at u from nearly any range within a second, even I a human (non ninja) cud throw a knife very quick, to do the ka Shisui will need to activate MS which takes at least a couple secs. Anyways, seeing a kunai come at u, first reaction wud be to block, not to sit there and blink after a 2-5 sec period. When Shisui blocks, Minato can appear instantly and rasengan him. Shisui can never even expect Minato to appear out of a kunai, and even if he does he may not be able to notice a seal that quick, once again that was why ppl were told to run away. Anyways once Minato appears Shisui is done, unexpectedly. So no Shisui cannot beat Minato along with many other powerful ninja. MS takes a while so u were wrong, so i believe Itachi will also lose since his genjutsu are short ranged. Of course there are ninja that can beat him though, Pain has a real good chance, and EMS Sasuke if he has more power than Itachi he wud most likely crush Minato and so wud Madara. Also Tobi wud def, and Naruto is pretty much there. I am not gonna overrate Minato but not overrate shisui either. U_U