Technically, what he's saying about KoTOR2 is right, but he's making the mistake of attributing its problems to Obsidian rather than the material it was working with to start with. Yes, in the Star Wars universe Kreia is an unrepentant villain, because Star Wars operates on only the most childish black and white morality, thanks to that whiny asshole hack Lucas, and the last leg of KoTOR2 is unfinished and shitty because Lucas Arts wanted it released earlier. They also had to use the lightside ending of KoTOR as cannon, because Lucas requires that every story in the EU end with the heroes triumphing, or at least not losing completely if it needs a cliffhanger to better sell a sequel.
Now, I've enjoyed Obsidian's games, though I've only played KoTOR2 and NWN2, but both were flawed and buggy, and I know at least the first of those was forced out the door quite unfinished. I've liked everything Bioware's put out since NWN better though (I never did play the first KoTOR though). NWN was a solid game, Jade Empire was good and unique despite its simplicity, Dragon Age is a brutal subversion of mainstream high fantasy (and yes, I'm sure there have been authors who also did that, so what? Are they all unoriginal hacks except for whoever used that general theme first?) and Mass Effect is only slightly kinder to its own genre.
Sometimes limitations, however, force you to think outside the box and make decisions that ultimately benefit the experience. Garrus, for example, wouldn't be nearly as interesting a character for me if he was such an easy convert to the ideals of ParaShep. Instead, he's naturally resistant, as his own nature pulls him towards the Renegade side of the Karma Meter. But through example and good leadership, Shepard can show him there's a better way; but it's not easy, and takes two games worth of work to get any lasting improvement.
If they'd let me make him a Paragon team player in the first game and let his character stay flat like that through the sequel, that would have been horrible. Planescape, as far as I know, didn't have a sequel. Mass Effect is stretching the story over 3 full-length games. That gives it far more time to develop its characters; Planescape let you wrap everything up in one game, but if we handled every last problem in the first Mass Effect it'd leave us with 2 games of no development whatsoever.
I don't see where you're going with this.
If I had unlimited resources and unlimited time, I'd've made it so that your actions in the first game had either made him marginally better or far, far worse (depending on how depressing you want to go). So, if you encouraged renegade, you make him be a bit harsh, but not too bad. If you encourage paragon, he becomes a real monster because he's rebelling against what you taught him. After all, you died.
The hell does that make sense? If you encouraged him to shoot the doctor in the first game, you're just reaffirming the decisions he already made, and if you stop him from doing so you are not letting the doctor go, but sending him off to spend the rest of his life in a cell, which doesn't really apply to any of his actions in the sequel. I'd say compared to some trivial, informal advice you give him in the first game, any events both before and after his time on the Normandy SR1 would be far more influential on how he acts. The issue of whether or not to kill his former comrade for selling out when he had a gun to his head would probably have more of an impact, but then again, just like the first game it's a single isolated event. A single event can lead someone to radically alter their behavior, or it could just be reasoned away with "well, given the context, that was the right way to act; this is different, thus requires different action," which is far more realistic a reaction than "OH GOD I WAS WRONG ABOUT EVERYTHING BECAUSE ONE SITUATION WAS KIND OF COMPLEX TO DEAL WITH NOW I MUST BE SOMEONE COMPLETELY DIFFERENT!"

Actually, you have to play Shepherd like a manipulative bitch who is so paranoid he upgrades everything. Manipulate crewmembers that you want with you, mainly.
What? You're explicitly told, repeatedly, to do everything possible to stack the odds in your favor. Upgrading everything you possibly can follows that logically. Going out of your way to throw your crew into extremely difficult, emotional situations a little less so, though in most of the cases it's "oh shit, this just happened, I've really got to deal with this before we all go off to die," so it naturally follows that they're going to be either resentful that you ignored them, or distracted by the unresolved business, and thus not on their best game.
What do you mean? The only way that happens in Mass Effect 2 is if you roleplay Commander Shepard as a total retard. I only lost 1 character on my first run, Zaeed, and every other time I pulled everyone through. And I got a Tali romance in the sequel, so the Neeshka thing's a moot point here.
How does getting to fuck a (possibly anteater shaped) space gypsy that's deathly allergic to
literally everything, especially you, make up for not getting the demon chick? Admittedly Neeshka probably smelled like sulfur, being a tiefling and all, but considering you could play a tiefling yourself...