The fantasy campaign was a sequel to a previous attempt that fizzled, in which the only PC that was carried forward was satyrblade's quasi-werewolf character. It was in a fairly eclectic homebrew world, in which the only "humanoid" races were elves (who were in hiding and only interacted with humans in disguise), trolls (who were basically orcs the size of André the Giant), and the werewolf race. (There were also mentions of vampires, but they never made a direct appearance.) Instead of the standard quasi-medieval Europe of most fantasy settings, the game was closer to quasi-Elizabethan, with pirates and intrigues, with rapiers and flintlocks supplanting the older chainmail-and-broadsword combination (which still existed, but was in decline).
The big thing that made the setting different from more standard fantasy game fare, however, was the extreme rarity of player magic. Phil's werewolf was the only character who was inherently magical in any way, and none of the characters had any magic rings, amulets, cloaks, etc. (laurie_robey's character discovered roughly 2/3 through the campaign that she was a half-elf and never knew it, but it didn't give her any special abilities.) Throughout the whole course of the campaign, there was only ever one magic sword -- roughly the equivalent of a +2 longsword in D&D -- and the characters were carrying with the intention of destroying it as it was. (It had the spirit of a dead king from the human/elf war bound to it.)
There was magic around. The PCs encountered more than a few cackling sorcerers, gibbering horrors from beyond space and time, and once all got shrunk to 4" tall so they could enter an elvish enclave inside of a large tree. (The attempt of one of the PCs to go squirrel-riding, alas, ended in a painful surprise.) But magic was rare and unique -- when you encountered a wizard it was always worrisome because you had no idea what he might have up his sleeve. Would he call down fire from the sky? Would he blast your brain with arcane power? Would he summon up some massive horror that would turn on him, have him for a light snack, then go rampaging through the city? The only thing you could count on was that it probably wouldn't be nice.
This campaign was run in Fantasy Hero, which was a major reason it was like this. The HERO System is a terrific system for building exactly the effect you want -- assuming you're good at tweaking the system (which I am). However, if you're a casual player who doesn't want to bother with the math necessary for creating spells and powers and such, it comes off as a massive headache. Thus, most players will just buy lots of skills and play fairly "mundane" sorts of characters ... e.g., warriors and rogues.
The reason this game was a success and held my attention, in a way that D&D usually doesn't, I suspect, is because this "warriors and rogues in a world where magic is rare and dangerous" is exactly the kind of setting in which I'd prefer to play. (It's hardly a coincidence that this would be a good way to describe a Conan campaign.) This kind of a game can be done with D&D, but it takes a lot of tweaking! Off-the-shelf D&D assumes that characters will have various booster items, magic weapons that punch through damage resistance and/or add damage due to having blades made of flame or frost or holy power or whatnot, and that the characters will have a wizard and a healer on hand. If you tossed a party of warriors and rogues sans magic items at an off-the-shelf D&D adventure, they'd totally kick butt against all the orcs and gnolls, then get instantly slain by the first wight or wraith they encountered.
The story-based structure rather than encounter-based structure is another factor. In the FH campaign, there was a lot of fighting, but it had a very different flavor from a D&D game's combats. In FH, there isn't as wide a power difference between the lower end and the highter end. Thus, a mook still has a decent chance of landing a debilitating blow. Against a party of four characters, a big fight would be two mooks each plus a boss. Even at the end of the campaign, I still used the base stats for the same mooks I'd used at the beginning, because the players generally spent their experience points on broadening or improving their skills, rather than cranking up their combat ability.
So what am I getting at with all this, beyond the obvious "So Gneech likes the HERO System better?" Well, this: I noticed that when I started working up ideas for my new Star Wars game, I was back to working on a story structure, rather than an encounter structure, because there isn't that much off-the-shelf stuff available for the d20 Star Wars game ... and I was enjoying it a lot more. My whole reason for switching to D&D, besides trying to make it easier for jamesbarrett to make characters, was so that I could run adventures off the shelf rather than having to spend a lot of time on the game mechanics of the thing. But I think, in the long run, this goal has been something of a wash. Even for adventures that I've pretty much run straight out of the module, I still end up transcribing all of the maps and encounter stats into a more easy-to-use format, tweaking a lot of it as I go, and running a bunch of stuff off-the-cuff.
I think, in my attempt to acclimate my GMing style to the D&D ruleset, I got a little too hung up on trying to make everything a "balanced, level-appropriate challenge" and such -- I got too into the numbers, and kinda lost sight of the story. I also spent too much time trying to customize the NPCs and opponents in ways that don't matter. The characters don't know what's on their character sheets, or on those of the people around them.
I also think, that the only way to keep my current D&D game from floundering yet again I'm going to have to (besides, y'know, actually PLAYING it again soon) remember to look at it from the point of the story. We've got the Guild of Arcane Path as a potential source of stories, we've got the characters' would-be employer in Bissel who can send them on missions (which they may or may not be up to completing, they can't know 'til they try), and in the background we've got Evard and his brewing plots. Surely there's got to be fun and interesting stuff to do with all of these, so I just need to think of what would be cool first, and then come up with the mechanical stuff to support that second.