When I first played Dragon Age: Origins, I left the first town, Lothering, before I had fully explored it and I missed out on Leliana and Sten. When I found out, I felt cheated. Two characters represented quite a bit of the story telling that I actively wanted to read! I probably should have noticed various subtle signals that I wouldn't be able to return to Lothering. I also felt cheated when [spoiler] I couldn't stay with Alistair because I was an elf! [/spoiler]
Another time I felt like I "missed out" was in Gabriel Knight: Sins of the Fathers. I found out that I could have returned a wallet I picked up for extra points, among other things. I felt both impressed that they included this detail and annoyed that it didn't follow other adventure game conventions where people don't care about their crap.
|yes, of course you pick it up
|what do you mean this was the appropriate reaction 2 hours of gametime later? [src]
I could have avoided this "missing out" if I had read through walkthroughs carefully. But as much as I like to plan things, I also enjoy not knowing what will come next. If never missing out on parts of games means never being surprised, I'm okay with missing out on a few things.
And perhaps it's more realistic to have some actions have big, unpredictable consequences (like what race you choose in DA:O). It's hard to simulate "fate" in a computer game, since the entire storyline is obviously "fated" by the writers. But when a decision you make turns out to affect more than just the immediate situation, it can give the world a richer feel. That is, as long as it's not a dumb decision like whether you choose vanilla or chocolate ice cream (an actual decision in the branching-path graphic novel Meanwhile that determines whether or not there's any story at all).