These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Dying Moment of Awesome: Besides Robert's Heroic Sacrifice, the Poseidon itself: when the ballast tanks finish flooding, it, now a ghost ship, rolls upright one final time before slipping beneath the waves.
Ho Yay: hinted at between Valentin and Richard. Valentin does end up getting it hard not long after, but not at all in a Ho Yay sort of way.
Narm: Not exactly right off the bat, but when Richard seriously tells Elena to grab a hold of his ankle it's funny when you realize the last time a person (Valentine) tried to hold onto Richard's ankle for dear life he was kicked off to his death. Of course, she ends up dying eventually, too...
The scene of people panicking, tripping, throwing chairs, and getting whacked in the head by girders in the disco is meant to be frantic and panicky, but comes off as unintentionally amusing. The last one, in particular, seems as if the ship said, "Screw you!" and smacked the guy on purpose.
So Okay, It's Average: Most reviews seem to agree that while the story and charachters are mediocre at best, the film's visual effects and action sequences are great.
Tearjerker: Richard holding the dead Elena in his arms. You really get the sense that he's come to think of her as a daughter in the short time he's known her.
Visual Effects of Awesome: The capsizing sequence is unquestionably the highlight of the film, but the Poseidon itself is amazing, as all the exterior shots of the ship itself are 100% CGI, and was listed in the 2010 Guinness book of world records as the most detailed CGI model ever to appear in a movie. And the opening shot? The only real element is Josh Lucas running around on the decks.