By the power of truth, I, while living, have conquered the universe.
85% of ME3 is running around the Galaxy Map scanning systems for alien space bibles and War Assets which have no impact on the game AT ALL.
After all the build up of the Rachni plot and the Queen's promise to help us fight the Reapers when the time comes, nothing comes of it. Where's the Rachni fleet that was being created in ME2? How about them helping us rebuild after the Relays are destroyed in Destroy since they're so technologically superior to most races? They're not even mentioned after their little cameo beyond a single slide in the Extended Cut which you only get if Wreav is the krogan leader.
And one of the biggest things that needs to be redone is the last mission. It was horrible. Words cannot even begin to describe how disappointing and dull it was, especially in comparison to ME1's race to the Citadel and ME2's suicide mission. All we get in ME3 is about a dozen Brutes being spammed at you while you move through some dark streets to fire a missile at a Reaper. There's no danger in losing anything or anyone, no variety in what can happen at all.
'Side missions'. Except they're not side missions, they're fetch quests which have you drive around the galaxy map to collect space bibles for people so they can fight the Reapers. That's it. I just summed up 85% of the game for you. Not only that but it's just weird now that Shepard eavesdrops on these conversations, then travels across the galaxy to find something that might not even exist, and gives it away all like it's nothing. There's none of the sophistication that ME1 had where side quests would actually interlink and could later reveal critical plot elements to you if you took the time to do them - the Consort/Xeltan quests interlinking and resulting in the Prothean Sphere being able to be opened later in the game to reveal the Prothean involvement with Cro-Magnon humans.
Then there's the levels themselves - most of which are -blam!- boring. Compare ME2's suicide mission to ME3's Earth one. In ME2 there are over a dozen different outcomes depending on what you did during the game - didn't do that mission? Tough, Grunt dies. Didn't buy that upgrade? Tough, bye bye Thane. In ME3, the last mission is just a Brute/Banshee-spamming Gears of War shooter-esque fight scene to fire a missile. That's it. There's nothing at stake, there can't be because you don't even see your War Assets which you spend 90% of the game obtaining.
Plot holes, inconsistencies and general screw-ups include the Human Proto-Reaper somehow being obtained by Cerberus even if you destroyed the Collector Base. Go back and watch the end cutscene to ME2, NOTHING survived that explosion but somehow most of the Human-Reaper is intact and is being rebuilt for some unexplained reason.
Where was the Trial that Arrival built up to? What was the point of ME2 at all? Instead of being given a detailed opening where you revisit your choices from the previous games giving you the ability to relive your whole Mass Effect career, all we get is Shepard looking at the Artistic Integrity kid and some koala bear-turned human called James is talking to you and then the Reapers arrive. It comes off like a script written, edited and used as a first draft by George Lucas.
Now other shyte stuff.
- Massive emphasis on auto-dialogue. Core of the game is abandoned, the player is no longer Shepard now that he starts acting out of character.
- The utterly contrived nature of the Crucible and the bull-blam!- surrounding that whole plot point.
- No Galaxy exploration. No vehicles. No little missions on the faraway planets. Consistent with Bioware ethos - "if people don't like it, completely remove it (unless it compromises our artistic integrity)".
- Abandoning the dark energy plot.
- No ME2 characters as a squadmates (other than Tali & Garrus) or even proper LI's, other characters like Wrex are just completely wasted. Fact.
- Killing off characters in emails and on Twitter.
- Crucible. 'Nuff said. This space microphone/deus ex machina is utterly disgusting.
- Choices did not matter at all. Rachni, geth, Collector Base, etc - all have no major consequence.
- Catalyst's existence.
- Overall plot is horribly weak and inconsistent - Kai Leng plot armour, Cerberus somehow becoming Stormtroopers and so on.
- Half-assed journal UI.
- The very idea of Synthesis is just a thematic middle finger by Bioware.
- "Artistic integrity".
- No Harbinger beyond a 30 second cameo.
- Tali's face.
- Diana Allers.
The other games have issues both minor and major, but ME3 is just... so bad.
[Edited on 01.08.2013 12:05 PM PST]