Heroism has always been a hard quest to go for. Not all people are going to be heroic, and in any situation where there's a good chance of randomness, simply too much of a mind towards survival, tactics or intelligence can kill the feeling of heroism. Unfortunately, I can't really tell you if the rules get in the way.
Things that make heroism difficult:
The first, and foremost is walking. I don't mean the aspect of walking. Walking from place to place is fine. However, there are the situations where I'm spending two sessions trudging through forest, desert, mountians or whatever else. When your only activites are a roll or two on the random monster table, and cutting down some rations, well, I stop feeling heroic. It's too easy to lose sight of what I'm really doing in those situations. Can't see the forest for the trees and all.
Negitive feedback. In the first session of a game I was playing in, the first fight was a story event we couldn't change involving monsters that, if they had seen us, could have destroyed the party in two rounds. The third fight left 3/4 of the group with about 3 points of con apiece. The fourth fight nearly killed a member of the group and inflicted status effects we couldn't cure. After that, we avoided conflict at all costs. By the way, aside from the first fight, this all occurred along a fairly well traveled area. You can be we weren't feeling at all like we were worthwhile. There followed that the only dungeon entrance was barred by a locked door the rogue couldn't open, we ended up spending an hour chopping it down. Inside the party was forced to retreat from animated furnature that nearly killed us. Did I mention not feeling at all worthwhile by this point? Another similar situation happened in a game I heard about. A player shot the lock off of a door, and tried to rush through it. But the door wouldn't open. Why? The latch was still down. In the same game, we spent weeks crossing the desert to find the one town that had civilization to find nothing of worth, not even a plot hook. The game almost died right there. And, just to show some more of the range, how about the game where my archer was in the dungeon of five foot corridors that lead into 20 foot rooms with creatures with piercing risistance. That sucked too.
Cool NPCs. In the above game, we were bombarded by the DM's neat NPC's. The town guard with the magic arrows who made a really impressive shot as we came in. The wizard who was hit by a death arrow for enough damage to kill the party. The cleric who defeated the band of imps that the party couldn't touch and started the darn quest. Heck, add the talking doorknob and the animated suits of armor to the list. Whenever we encountered these things, we just ended up feeling plain and unimportant. "Don't mind us, officer, just a band of level 1 characters here."
Bad parties. In one game, we had a guy who seemed to follow the party around, even though he hated them all and wouldn't hesitate to sell us all out. In another game, we had the guy who complained about every course of action. In another game, we had the loner, captian angst, and a greedy bastard all at the same time. That was also the game with the famous line "You can't just go around being a hero! Being a hero is not a job! Heroing is not a word!" The people playing your game can kill things before they start.
It's easier to be heroic when I have some belief that you'll succeed, and when I believe my actions will be relevant. If I'm just delivering a box, it'll hardly be important.
Choice is an important issue to. If it's somethign that's being done for money, or because 'nothing will happen if I don't' then it doesn't feel nearly as heroic. When the course of action is one that the players decide upon, then it has the potential to feel a lot more heroic.
The most heroic thing I ever did was climb down a rope. Mind you, the ground had just collapsed and two of my party fell with it into the unknown. So I grabbed a rope, tossed it to the strongest member of the party, told him to brace me and climbed down.
Unfortunately, I rolled fairly poorly (a 5) and fell. That was the last heroic thing I did for the next few months. I think the fact that I didn't die from the fall, though I should have, had a lot to do with that. Had I died, it would have meant something. But, as I got back up with 2 hp left and a movement penalty, it hit home that, in essence, we would survive anything, and that we were just sort of being strung along.
Ah well.
But yeah, find people willing to play in a heroic game, reward them for it (early successes without twist or malice). Build them up so they know their strength, or determination, or at least relevance.