There is an interesting thread over on the SJG forums about choosing a "DF" game (GURPS Dungeon Fantasy, a roguelike with pen and paper as my player described it) or a "fantasy" game (a much broader game.)
A somewhat tangential discussion has sprung up about what I refer to as a player-GM wants mismatch. That is, what the GM wants to run and what the players want to play doesn't overlap.
Basically, what if you provide the players with a game that rewards exploration, politics, and diplomacy and downplays looting dungeons, but the players show up session after session and just want to loot dungeons? Or vice-versa, although I suspect that is rarer ("But I wanted to negotiate with the ambassador from Nextdooristan, not fight the dragon! Lame!")
It's not only this type of game. If you provide a hexcrawl and the only things the players want to do is find a hex with a dungeon near a hex with a town and stay until they've cleared it, you've got a similar problem. Or if you set up a megadungeon and the players just poke around on level 1 and then leave, hoping to explore the world you didn't bother to populate or map. Or you give them a starship to explore the universe and they plunk down in the nearest starport, buy a bar, and serve drinks.
It's tempting as the GM to punish the "wrong" behavior. "Killing the orcs in the dungeon is illegal, we have a treaty with them. And the crown claims 50% of the loot as taxable income, plus a 100% penalty for your crimes!" Okay, sure, but if everyone signed up intending to play orcslayers?
It's not railroading (although it can be). It's really a mismatch between the game the players want to play ("In this world, it's okay to go into tunnels and fight monsters and take their stuff - in fact, it's expected that we do this") vs. a different expectation from the GM ("In this world, dungeon-bashing is illegal, impossible, or sanctioned, and you will be rewarded for exploration and politicking.") What the players want and expect to do is different from what the GM wants to run and expects the players to do.
So what do you do if you've got some awesome ideas as the GM, but the players have a different idea of what is fun?
The only solution I have for this, besides "find a game you all want to play" is to offer hooks to the players to draw them into the game you'd like to run, and reward them if they bite.
That's very different from punishing them if they don't.
An example of punishing might be: "You loot the dungeon, and now thieves have moved in and started raiding the neighboring country, starting a war. If you don't act as diplomats and stop the war, it'll impact your every action. Prices rise across the whole country, it's not safe to wander around looking for dungeons, people treat you funny because they assume if you're not on their side you are mercs for the other side, and all of this lasts until you get involved in the politics!"
A better offering rewards might be: "You looted the dungeon, and now thieves have moved in and started raiding the neighboring country, starting a war. You're responsible and the King's men require you to lead a punitive expedition against the bandits, and repel the attack of the neighboring country. The diplomats will smooth it over, but only if there is a victory. Of course, if you choose to act as the diplomats, there are some additional rewards out there . . . titles, influence, social power . . ."
The first punishes the players for doing what they want to do in the game (bash, kill, loot) without doing what you'd like them to do (politic, negotiate, travel). The second lets them do what they want (bash, kill, loot), and then offers them more, with a bonus if they do what you'd like them to try doing (politic, negotiate, travel). Both feature a living world, but only one of them forces the players to spend time on stuff they don't like in order to do the stuff they do like.
Essentially the idea is, keep putting the possible upsides and interesting in-game complications, and the fun there can be in resolving it, in front of the players. Keep baiting the hook and let it dangle. They may bite. If they don't, and you're really not having fun GMing the game they want to play, end it and move on. It'll end either way; you may as well end it before it gets ugly.
My previous campaign had a lot more plot and politics, although nothing really forced on the players. Generally they got what they asked for and then some - it's just that they often asked for trouble. It was a lot of fun, and lasted for years (1999-2010, although while I was living abroad we only got in a few sessions a year). Still, we got burned out on "the big campaign" a bit, so when the game ended we didn't pick up a new game. We took a break and played board games for a while until we tried a DF one-shot. That scratched the fantasy gaming itch in just the right way for us, which is why we've got 30-odd sessions under our belts and have been playing since late 2011. It's the game we all want to play. I think, in the long run, that's the only kind of game that will last.