I suppose that I'm one of about five people who likes Gothic 3 more than than the previous games, however I have no problem admitting that it's not a perfect game.
I'll address some of your points...
1: The game does lag and stutter, a lot. There are no loading screens in the world and the world itself is pretty large, hence the lagging. With the community patch it does lag a lot less, and in some areas it doesn't lag at all, but some places will always lag and stutter, unfortunately
2: I prefer Gothic 3's control system. You could say that it's been simplified, but I like it a lot more than the previous games controls, which I found to be...clunky, to put it politely.
3: I don't think you can say any of the Gothic games (or the first Risen, haven't played the second) have good dialogue, or a good story for that matter, and to me Gothic 3's dialogue is no better or worse than the other games in the series. I'll agree that the dialogue can be pretty bad and silly, but like I said, that seems to be the general rule in this series.
4: The main goal in the beginning is made pretty clear, you need to find Xardas, I think if you talk to Milton after the tutorial Nameless Hero outright says he needs to find Xardas.
5: The Orcs in the tutorial are weaker than the normal Orcs because, well, it's the tutorial. The game does have some difficulty flaws (like getting stun locked) and some things that don't make sense like a Warg taking on an entire bandit camp and winning.
Admittedly it's probably just a difference in taste, but I really do prefer Gothic 3 to Gothic/Gothic 2/Risen and it's not even close. If you want to give Gothic 3 another chance, be sure to use the latest community patch. But hey, if you don't like it then move on to the next game, considering the reviews of Gothic 3 and how people in this very thread are talking about it, you're probably not missing much if you already don't like it.
Post edited May 23, 2014 by NoNewTaleToTell