Single player is essential for me; multi-player is optional.
I'm no use at quick reaction games - even the slightly more advanced melee system in "Age of Pirates - Caribbean Tales" caused me problems. The system in PoTC suits me perfectly.
Generally I prefer third person because it's easier to see around you, so you can see things which in reality you'd know about by a quick turn of the head but which in first person you need to swing around to see. But the ability to switch at leisure between first and third person is nice, then I get the immersion value of first person plus the overview value of third person when needed.
For me, isometric is really only for pure strategy games.
Quests should not be blatantly signposted. The punctuation marks floating over NPC heads in AoP were just silly.
All of which are contributing factors to the conclusion that what I want to see when playing a pirate game is the PoTC New Horizons loading screen.
Back to quests, though - does anyone else remember the old game "Mercenary" on the Commodore Amiga and Atari ST? Nothing to do with pirates - this was a sort of science-fiction adventure game with first person wire-frame graphics. Then there was the sequel, "Damocles", with fully shaded graphics. The plot in "Damocles" was that a comet was going to smash into a planet and you had to stop it. The way to do so was very clearly signposted. Except that if you dug a bit deeper, you could find several completely different ways to achieve the final objective which weren't signposted so well, or even at all. Writing a quest in a similar way, with one blatant way to do the job and four or five other ways to do it that aren't so obvious, would be a pretty good trick, but would make the story much more interesting, especially if you've played it through once and are wondering what to do next time you play the game.