Christmas Ape wrote...
Because Mass Effect ended on a high note, then they kicked you in the junk and took your hat. Everybody came into Act 2 feeling buoyant, settled into their seats, and got jarred by a sudden key change.
You end the game with a hell of a reputation, you almost single-handedly dragged humanity into the galactic spotlight, and you and your ship full of BFFs have been through absolute hell, proved yourselves to each other, and averted the end of civilization. You're a legend.
Then BAM! Mass Effect 2. Say goodbye to all of that, but your obituary is beautiful - if premature. Your new allies aren't Space United Nations, they're Space Ultranationalists, and it's only your reputation that keeps you from being a wanted criminal - you must have a reason. You're tossed under the bus of political expediency by the Powers That Be with an implicit "don't call us, we'll call you". Your team is scattered to the four winds, and the intervening two years have changed them. You'll need new people; new people willing to die.
Sudden key change, major to minor.
You're not on detached and illustrious service with humanity's military, you're running errands for their dirty secret. The story picks up speed, shoving a problem in your face a few times instead of having it wait for you, and shifts focus from the investigation to the investigators. You're staring down a suicide mission and sharpening your team for it - it's as much about them as it is about you or the enemy.
Sudden key change, major to minor.
Most importantly, however, is that this time nobody expects to come back. Mass Effect had a sense through almost the entirety of it (at least until 4 plot worlds are done), especially in conversation with your squad, that victory was inevitable. Just a matter of time before you find the enemy and bring him down. Mass Effect 2 is entirely in opposition to this; you're going to have to throw yourself into unknown hell to even take your shot, let alone go home.
Sudden key change. Jarring. Effective if you get swept up in the new movement, something you sit bitterly chewing on the whole night if you don't.
Everything else is complaining a game straddling two genres didn't slavishly devote itself to the cruft of one of its parent genres but instead tightened its focus on the other, being unable to tell one metallic endoskeleton from another, wanting the middle act of a trilogy to explain everything, or being unfamiliar with the more horrific theoretical transhuman outcomes.
But I think a lot of it is, in fact, "But...but...I won Mass Effect! I'm the hero! BAD THINGS DON'T HAPPEN TO ME!"
This same thing happened between Star Wars and Empire Strikes Back. However, there wasn't the internet to stoke unreasoning nerdrage so I didn't hear any negativity about it. It that movie, Luke lost his whole team except R2 and didn't reunite with them until a brief scene at the end. His middle movie was one about self-discovery.
The story in ME2 is character driven and gritty. It's not a sweeping Star Wars space opera but a gritty, revealing middle chapter Empire Strikes back.
My major complaint after reading through this forum the last few days though is that while I praise Bioware for listening to criticism and delivering much of what fans begged for (Garus romance, Tali romance), it created a cadre of spoiled children who think throwing a temper tantrum over every tiny detail that they don't like will avail them something.
It's Bioware's story. It's their game. I think it's been brilliant but then again, I just sit back and enjoy it instead of tearing it apart because I would have painted the walls a different colour in the bathroom.