About the feel of an X-Men game. I played in one of those, we were a younger generation of mutants, on our own 'team'. And yeah, the general populous didn't really like us. This was the game where I spent upwards of half hours brooding darkly about the small-mindedness of people, and purposelessness of my actions. There was a lot of the team pulling together to help pull whoever was having a bad day out of the gutter. My character was leader of the team, and his main goal was to keep his sister and his friends safe, no matter what. It was a blast, but it was a sad, dark game. The is also the one where my 'calculating action leader' half turned evil, fell for a demented psychic, and joined Apocalypse's forces after the death of a friend.
Yeah, the game was a blast. But it was also set up for that dark brooding atmosphere, where we were all outcasts. We were all eachother had. So the world was set up for that. And we still got rewarded for playing into the game. I had a talk with Cyclops about leadership, that was cool. I got fighting tips from Wolverine. That was cool. "Good job, bub." We were still congatulated, we were still warmly encouraged. It just wasn't from the general populace (who, in this case, were mostly backdrop anyway). It was from the people important to us.
Now feedback is important, and, in every D&D game I've seen, there are two major social ways to get it. The first is from the populace. The cheer of the town as you come back proudly bearing the kidnapped children is a wonderful thing. The other tends to be from affiliated orginizations or patrons. This can be more satisfying, especially if the players care about what their patrons think. In all the games I've played in though, the patrons were a set of people who gave missions, and weren't really allies. Just a source of gold. So their opinion was pretty much out. That left the population. When we didn't get props from them, the game just got kind of depressing.
It's not such a big deal if you've got other ways of positive re-enforcement. But in the games I've run, seen, and played in, the most common sort of re-enforcement was via how people reacted to us.
In short:
1. Set up the world to maintain the feel you're shooting for.
2. Set up ways to reward the players for doing well.