Most people will point to the ending, which I certainly think is lackluster at best, but my problem with the game is more emblematic of the series as a whole. My favorite part of the second game was the series of recruiting and loyalty missions. There's an overarching plot about an implacable alien force called the Reapers, who periodically attempt to destroy all life in the galaxy, but I always found that aspect of the story somewhat trite and boring. To me, it was only interesting in so much as it gave me a reason to recruit my crew. It was a unifying evil force in the galaxy, so it worked, but it wasn't all that special or interesting. So the second game focused a lot on your crew, gaining their loyalty through side missions, and stopping some Reaper-related threat. All is well so far, so where does the third game fall down?
Well, at the end of the second game, your crew is scattered and you end up starting over. This is a minor instance of the Video Game Sequel Problem, but one of the interesting things about the Mass Effect series is that your decisions from the previous game play into the current story. That being said, you kinda have to start over. My biggest issue with this third game, though, is that you're not really building a crew that can defeat the reapers. You're trying to align galactic resources, playing politics to get various races to cooperate, gaining strength for the coming fight with the Reapers. There really aren't many new characters, and most of your former crew are relegated to supporting roles, cut scenes, or temporary missions.
The end result of this structure is that in the second game, I had built a crew of 12 members, each with their own personal backstory and independent, often interesting loyalty missions that illuminated their character. In the third game, I had a crew of 4 or sometimes 5. A few of them are characters I know and welcome: Garrus and Liara. EDI is the ship's AI come to life, which is a great development. Towards the beginning of the game, when this happened, I found it very encouraging. Unfortunately, she's really the only new character that's really interesting and progresses through the entire story. Gone are the recruiting and loyalty missions where I grew to like all the characters. Heck, even Shepherd's choices seem to matter less. The whole Renegade/Paragon thing seems to matter much less here, instead you get "Reputation" points, though it's unclear what that actually means (and I'm pretty sure it doesn't mean anything in the end). There are some side characters who showed promise, but they were either relegated to a small part of the game or they didn't have a lot of depth. For instance, I enjoyed playing chess with Specialist Traynor, my Comm officer, but that's really where her role ended (apparently she's a romance option for female Shepherd).
Actually, my romance option from the second game was Tali, and she does show up for a while in this game, but I think some of the choices I made lead to her death (I had, essentially, chosen not to commit genocide against the Geth, but wasn't able to broker a ceasefire between the Geth and the Quarians, so a lot of Quarians ended up dead and Tali committed suicide). This was a tough mission, but it sorta fit with the game and I can see why it happened. Inexplicably, Tali shows up after her death for one last go, just before I went to the final battle with the Reapers.
Anyway, the focus of the third game is to build up Galactic Readiness, aligning alien factions, many of which have longstanding grudges against each other (the Geth and Quarians being an example). This is all well and good, and the whole resolution to the Genophage is actually very well done, but while I got to spend some time with Mordin and Grunt, there was very little moving the characters forward. This seemed to happen with a lot of my former crew. I got to see what became of Jack, which was pretty great (she's grown as a character between games, which was really nice), but it's not like she joined the crew again or anything. Other characters showed up too, but it was all ultimately unfulfilling. It was all in service of fighting the Reapers. And, I guess, Cerberus... an organization I've never quite understood, though I must say that the Illusive Man certainly shows more personality than the Reapers, and thus defeating his plans was somewhat fun.
I think part of my issue with the whole Galactic Readiness angle is that it's not entirely clear how much that helped, especially when you get to the ending. Indeed, the gamemakers even forced me to fire up the multiplayer missions in order to boost Galactic Readiness - though, actually, I really enjoyed the multiplayer for what it was - but while I got to see the pretty numbers increase, I never really saw what impact it had.
So the ending. It's a non-sequitur. It doesn't really logically follow what came before it. Since I wasn't that invested in the main storyline, it didn't actually bother me that much. I was much more bothered by the lack of focus on characters throughout the entire third game. The ending only exacerbated that complaint for me, though it's pretty bad in its own right. As usual, Shamus has done an excellent job breaking this down, in particular the parts about the Reapers and the Galaxy are insightful. There are, of course, contrarians, and I think there's an interesting discussion to be had about the authorship of video games. Devin comes down squarely on the side of the writers at Bioware, but video games as a medium are interesting because of interactivity. Because we, as players, have some sort of ownership of what's happening on screen. There are certainly limits to our ownership, and I think I might agree with Devin about certain pieces of this, but it's an interesting topic of discussion. It gets at the heart of the video game and storytelling problem, the thing that Roger Ebert keeps wanking about (interestingly, both Roger Ebert and Devin Faraci are primarily movie critics, so it makes a bit of sense that they'd side more with the creators than the players). A quick summary of Ebert's argument against games is instructive:
Video games by their nature require player choices, which is the opposite of the strategy of serious film and literature, which requires authorial control.This, of course, has been debated ad nauseum over the years, but then, it's the core of the problem with Mass Effect 3.
I am prepared to believe that video games can be elegant, subtle, sophisticated, challenging and visually wonderful. But I believe the nature of the medium prevents it from moving beyond craftsmanship to the stature of art.
One of the reasons the series has been so successful is that Bioware promised that our decisions would matter. Not only would they matter in the immediate story, but they would be accounted for in future games. This is astoundingly ambitious, and I enjoyed most of the game... right up until that ending, which just doesn't logically follow from the rest of the story. It's not just that my choices weren't taken into account - I don't think I would have been frustrated at all if that were the case. I understand that the nature of branching decisions would result in an impossible task for Bioware. There's just no way they could account for everything. But that doesn't mean they should account for nothing and completely change the whole purpose and goal of the story, all in the last minutes of the series. This could have been a game series that settled the whole Ebert debate in favor of video games... instead, it just gives the Ebert argument more credence. The reason people are upset is that it didn't really need to be that way. It's not like Bioware wrote themselves into a corner. There are a million possible endings that would be better than what we got. Dark, happy, depressing, confounding, whatever. It would have been better than "stupid", which is where we're at now.
Ultimately, I had fun with the game, but not as much as with the second game, primarily because of the characters. This whole grand overarching storyline was always underwhelming to me, but I had fun with the characters. Unfortunately, the third game disappoints on that front. The combat is good, the dialogue is well written, a lot of the big conflicts in the series are actually resolved in a satisfying manner... the game plays well. There are some things that aren't as successful. For some reason, the notion of "slow motion" Shepherd seems to fascinate the developers, and those sequences are annoying. I'm still frustrated that navigating to different decks on the Normandy requires a load screen each time. But those are nitpicks. The real trouble was the lack of emphasis on character, exacerbated by a non-sequitur ending. Again, I had a lot of fun with the game, so to me, the ending didn't ruin the whole series (as some folks are saying). Indeed, I find myself contemplating a second play through (starting back at ME2 with the Interactive Backstory (if I can figure out how that works)), perhaps as a female Renegade Shepherd.
Update: Just wanted to point to this video, a very long explanation of why the ending of ME3 doesn't work for him. It's sorta done in the style of those Red Letter Media Plinket reviews, but it's pretty good. The part where he talks about the Lair of the Shadow Broker DLC (from ME2) and how "Sometimes I'm not sure Bioware understands the magnitude of what they've done here" is particularly good, and it gets at exactly what I loved about ME2 - the characters! I don't know that Bioware recognized how attached players were to the characters...