The 'gory melee finishing moves' are just that. Fun finishers if you WANT to do them. The gun sighting seems to be completely up to you, as I've yet to use it on any of the few weapons that actually have it. In fact, it seems to be more like an eyerolling "LOL! Look, we can do ironsights too. Pointless, aren't they?" thing than actually being useful. Your gun will work just fine without them.
As for hyper-realistic graphics, I have no idea what you're talking about. I just can't reconcile the words 'hyper-realistic' and 'exploding suicidebomber without a head, which still SCREAMS at me!'. From the gameplay I've had so far, it seems to be exactly what a Serious Sam game should be. Just balls out mayhem. I do like how the weapon you're using starts getting more and more bloodcaked the more giblet explosions you are close to. A nice little 'immersion' bit there.
Sam seems to be just as over the top macho as always, without devolving into Duke Nukem's 'durr hurr titty humor' juvenile standards. (Don't get me wrong, I LIKE Duke Nukem's juvenile macho approach, but it's refreshing to just have John Rambo, The Terminator, Duke Nukem and Every Badass Known To Man's collective lovechild on screen being just utterly insanely uber-macho in all things.
Small spoiler: During the first level, Sam's got nothing but his own two hands and a sledgehammer and in the distance a GIANT devil-like fellow stomps along the street and glances in your direction. Sam's immediate response being "Whatchoo lookin' at?!" made ME believe I could have beaten that guy in melee. I probably couldn't have, so I'm glad it just kept walking, but it just set the entire tone of the game.
Should I manage to tear myself away from Skyrim and Saints Row for long enough to get through most of this game, I'll give a quick review of it. For now, I'll just give my first impression:
Serious Sam just got Serious... again... srsly. Fuck MW3, fuck Halol, fuck Gears of War, fuck all of the posers and weaklings out there. This is FPS gaming as it fucking should be!