I guess you've never played older games like serious sam 1 and 2, or old doom.. they had shitty graphics, but it was a fun experience..
the fps gameplay is pretty on par with those, the guns are accurate and most are fun to shoot the enemies with.. I've had more fun just running though level shooting stuff, than probably the rest of the game content..
especially with the light machine gun.. god.. 100 round clips.. that one is fun times!
as for the story events, ichika and kirara are really the only 2 that i really gave a crap about.. they have funny conversation sequences.. and ichika, to me, well I like her body type too..
x-ray has cum, it's just a single shot, as far as I can tell..
the girls never died so I didn't see the death sequences, but I wouldn't expect a sexy time if they are going to die.. one thing for me though... I never played the first game, so that's probably why I have that view opposite of yours.
..I'll say that from the decription you typed.. the first game's death scenes sound quite sexy though.