GAF, I just finished Contrast, and I can't think of any other game that burned all potential as hard as this game. Let me elaborate:

The gameplay is absolutely unique (or I just haven't heard of other games using shadows to progress through levels). There were certain areas in the game where I was standing around for like 5-10min thinking about how this step is going to work. But it was the kind of waiting that was fun because I was not like "awful fuck, not this again".

BUT. And this list is much longer.
What happened to the play time? I went through in about 3 and a half hours, collecting all collectibles (including luminaries). Why? Especially Act 3 was a hell of a lot of fun ( while Act 1 and 2 were too easy) and then everything is suddenly over. What a shame, I could cry.

Talking about luminaries. You need some of them to power certain lights or machines to progress, but you probably don't even need 20% of all of them. Why do they even exist? Force the player to collect more of them and create more puzzles he has to solve. While avoiding repetition, of course. They had a "good hand" of creating a big diversity of puzzles (e.g. the theatre play in Act 2) so I always had the feeling of solving something new.

Another point is the linear level design. While I understand this, I often thought about multiple ways to reach my goal. I'm talking about certain areas where you should have a choice between 2 or 3 puzzles to move on.

I can think of many more small ideas to improve this game (or a sequel), and as I said before, it makes me sad to think of what it could have been. It's a great game, but it seems totally rushed.

How about your biggest missed opportunities when it comes to games, GAF?

I hated it that in the Kingdom Hearts games that the worlds were so empty. I wanted it to be big and epic and see towns where there are really living more than 5 people. Putting in 20 more random strangers couldn't be that difficult?

Oh well there is always Kingdom Hearts 3 I guess

For me I don't think it's so much a missed opportunity in a game's design, but I have games that are well received but just don't click with me at all, and I'm always wondering what it is I'm missing about them that everyone likes. Recent examples are Fire Emblem Awakening and Mario 3D Land. Spent time with both, they're well-made and everything, I just didn't like either one of them much at all and I can't sort out why.

Recently played Remember Me.

End Game Spoilers only read if you played it or don't care about the game anyway:

For those that didn't play it, the game revolves around a network/corporation that stores peoples memories, to "save" them. Unfortunately you can either keep them for yourself or "save" them, not both. You play as Nilin suffering from amnesia, who is able to go as far as being able to "remix" memories, effectively changing the past in peoples minds without them noticing, to progress in the game world.

So to cut a long story short:

SWTOR should have been KOTOR III instead of WOW clone 27 with NEW HAT!

Such a monumental waste...

NSMB2 - The coin rush mode could and should have been something special especially if they had gone down the "daily challenge" route. Even offline it should have worked but the random selection of levels ruined it as a ghost house would derail your high-score attempts, to make matters worse the high-score was capped anyway.
The DLC hinted at what could have been.

Sleeping Dogs - It was a great game but it could have been even better if you were forced to chose between The Triads and The Cops somewhere near the end. Most of the game felt like it was leading to that moment but it never came.

Halo 3: ODST was such a huge wasted opportunity. I loved the atmosphere they achieved in New Mombasa, the music, the visuals, the mood while exploring the city, but there was shit all to do in it. Sure, there were Sadie's logs and some easter eggs, but the whole setting seemed underused.

The gameplay, too. For all its subtle differences, it was too similar to your usual Halo. Now, I understand they didn't want to alienate the user base, but there was a big opportunity to go in more of a, say, Deus Ex direction, to flesh it out more and make it feel more distinct. Exploratory parts of the game didn't feel rewarding enough, and they clashed with the flashback sequences which played practically like every other Halo game out there. And why did all the characters play exactly the same? There was a big disconnect between the cutscenes where they tried really hard to distinguish the different members of the team (they only partially succeeded, in my opinion), and the flashback portions in which you got to play each of them only to discover that they all felt more or less identical. The Superintendent AI was also grossly underutilized, especially considering how prominently it was featured in the game's marketing campaign.

In fact, I'd say that the setting and the story potential in all Halo games remains underused. There are so many small things they could do to make the world seem more alive, bits and pieces of background information they could scatter around for those willing to look for them (and hell, even in the menus and loading screens, why not?). A good RPG developer could do wonders with the setting. And don't force this ridiculous overemotional stuff on us, flesh out the world more, give characters more identity in the gameplay portions - not cutscenes - and the emotions will follow naturally. Play Half-Life 2, developers, it came out way back in 2004, for Christ's sake.

Killzone SF. If the rest of the game was like Chapter 2 (wide, open areas) then it would've been much, much better.