I've been thinking about an interesting problem in my exploration of game design. The problem is easy to explain but difficult to solve. Put as a question, how do you make every moment of gameplay seem to have a relevant a impact on the story? Not just the big picture of a mission(or level or whatever) like "go find X person," but every part of it. The reason I'm bringing this up is because a lot of games seem to suffer from large amounts of gameplay which feel like filler. You feel like your character isn't taking the quickest route between points A and B because the game developer came up with contrived reasons for it to take longer. I'm not just talking about games with choice. Whether the player is actually making choices that impact the plot or not they need to feel like their actions are important and make a difference.
How do we get around this? There will always be room for games like Portal that are short and sweet, but I'd be a fool to say that there isn't plenty of space for longer games as well. Typical side-quests in games with RPG elements seem to be the biggest victim of this problem. Many players complain about stupid, irrelevant and otherwise ridiculous side-quests which seem to be there merely to meet the required play length. This is looking past the real problem. I'm not saying side-quests are bad. Obviously if a game has good mechanics you're often going to need a lot of hours of gameplay to fully experience and enjoy them. I'm merely saying that designers need to be trying to make every moment of gameplay seem like it makes a difference from the outset.
A good example of this being handled at least a little is the way loyalty missions work in Mass Effect 2. Completing a loyalty mission for a character has immediately noticeable ramifications which continue to have effect until the end of the game. On the other hand, most or all of them can be skipped for people in a hurry. Additionally, all throughout the(good) loyalty missions you feel like you're actually advancing and effecting the central story, not just taking an intermission from it to complete some irrelevant mini story or play through a soap opera about another character.
I guess one of the reasons this sticks out to me so much is that I get bored of repetition in a game really easily. I usually only play games through all the way to the end if they're really good, and then I almost never play through a second time. Upon reflection, I think it is largely because I grow bored of central mechanics a little faster than most, but not if they're mixed in with an interesting story I feel like I'm helping to progress. Every time a game gives me an objective and then moves it around over and over again adding random and often laughable excuses for more gameplay I lose more interest and lost more suspension of disbelief. This is one reason I brought up Portal. Portal wasn't just short enough to stay fresh, it also lacked the usual nonsense and contrived excuses for gameplay time stretching.
I've been turning this idea around in my head for awhile. The reason I've held off posting about it is because I don't have any solid way to solve the problem. This is because it's not the kind of problem that has a magic bullet solution. Every game can and will deal with it differently. That's what the game designers job is, to find creative ways to get around and deal with the problems inhibiting their central mechanics. This is merely another one to be aware of. Perhaps sometime in the future I will discuss this more, it really is very interesting to me.