In no particular order...
Duke Nukem Forever
Lets get the big and obvious out of the way first. An FPS from the old age coming out in the present generation? Maybe I'd escape regenerating health, 2 weapon limits, 3-4 shot deaths with rapid firing weapons and a bunch of other crap that's in modern FPS. It somewhat did some of them, but at the same time... It just didn't work. At the start I found it alright, the puzzles were something different that I've always enjoyed in games. Something other than constant shooting to do, and there were a couple of fun gameplay things that popped up, but eventually its poor optimization, overly crude tacked on humour and just general poor gameplay got to me, and I stopped playing.
Mass Effect 3
Another big one out of the way first. There was very little that 3 did better than 1, or even 2. Shooting was about it, and even that was disappointing as it was still just a, more polished, linear corridor shooter. The story and level design went down the crapper further than in ME2, dialogue mostly disappeared, choices equated to nothing and the ending was downright bad. For something I was so excited for, it basically killed my interest in the Mass Effect series. I may eventually reinstall and replay ME1, but I have no interest in the rest of the series seeing what 3 failed to bring to the table.
Dragon Age 2
Really, this was pathetic. I'm not going to argue that combat in Origins needed to be better balanced, and made just a little faster to be more interesting - it really did. However DA2... Completely the wrong way of doing it. Enemies were action game enemies, you were a mix between an action game hero and an RPG hero, and it turned out poorly. The lack of unique areas also bought the game down massively, and whilst the story wasn't really bad, it was really just a bunch of faffing about until the end. Companion customization was gone, and many things in Origins that were not executed the best, but were still interesting were simply removed rather than fixed. The game could have been average, had it not been so incredibly rushed. I cautiously await DA2 to see if Bioware have learned, or not - like with ME3.
Skyrim
Forgive me everyone, for I have sinned. I haven't played much of TES series beyond a couple of hours in Morrowind at a friends house. Skyrim was hyped to be a large, open world RPG full of interesting things to do set in a Viking like setting. It managed the open world bit, mostly, and there was stuff to do, though not interesting, but overall it was severely disappointing.
Firstly, it was nowhere near as large as I'd been thinking it would be. IMO it seemed smaller than Tasmania, and for a whole province of Tamriel I'd expected it to be larger. Of course, there are limits to what videogames can do, so I was fine with this.
What really got me, however, was how dead the world was. The AI was just... uninterested in anything. Townsfolk and civilians were boring and largely lacked personality most of the time, anyone with any personality, no matter how important, only maintained it for a short while, the quests were short and relatively uninteresting, and the dungeons were amazingly repetitive. Dragons, instead of being something awesome to go kill, became the equivalent of Ogres in DA:O. Originally you're like "Wow, Ogre, its a boss or something, awesome!", and then you're like "Ah, and ogre. Great, one enemy that won't die instantly. Might have to hit it twice". Upping the difficulty didn't make it more interesting, simply more tedious to do anything. After being so excited for it, I was severely let down thanks to the simplification of it compared to previous titles, loss of features such as custom spell making, and how dead the world was overall.
Battlefield 3
I thoroughly enjoyed Battlefield 2. IMO it got the pacing right, its maps were good, I liked the classes and most importantly it had single player for if I got sick of the people online. BF3 dropped the ball.
It looked great, and I like the idea of weapon mods, but in other aspects it just failed me.
Vehicle mods was one of them. Planes, missiles and flares. You need flares to be half effective in an aircraft, yet they're an unlock. Yeah, they're the first one, but that's not helpful if the second you lift off you have 3 missiles locked onto you. You're just screwed in cases like that. It upsets the balance of the game in favour of those with the unlocks, as all vehicle unlocks IMO do. Weapon unlocks do too to an extent, but not as much as the vehicle ones.
Map design is terrible. IMO it tries to base itself largely around set pieces as opposed to being a good map. Bases are far too close together in most maps. The majority of the map itself goes to waste because there's no reason to be there - the bases are just stuck in the middle. This is slightly alleviated in the Back to Karkand maps, thankfully, but that's not enough.
Its too fast paced compared to 2 IMO. The speed at which everything dies... isn't fun. I have never liked 3-4 shot kills with assault rifles and SMGs that fire over 60 bullets a minute. It means if someone sees you you have less than 2 seconds to live. That's not fun. That's hide and seek with who sees who first.
And most of this I wouldn't mind too much if there was single player with AI on the maps because the AI doesn't really know how to exploit these things to make the game boring. Sadly, no such option existed, and thanks to severely weighted teams online, I lost all interest in the game a while back. It had some potential, but was really just... bleh in the end.