Previous games in the Fable series have had a history of promising more than they can deliver, and Fable 3 is no exception. While ostensibly about coming to power and ruling a kingdom, the shallow delivery and simplified gameplay make it less complex and interesting than it needs to be.
Like previous games, Fable 3 puts the player in the role of a "Hero", who can be customized and affected by various aspects of their character, such as their combat style and moral standing. In this game, the "hero" is a prince or princess rebelling against their corrupt and evil brother. The goal of the game is to claim the throne for one's own, although this eventually turns out to be the same linear quest-line that the other Fable games have used - there's no opportunity to recruit allies on your own, you just get what the plot provides for you.
In previous games, advancement was done by spending EXP that you earned by doing different task types. In this game, you get "guild seals" through combat, interaction, and quests, which you use to unlock new abilities on the "Road to Rule". The RtR is a linear path that opens up as you progress through the game, meaning that you can only go so far at one time before you need to do more plot/story stuff. This extends to a bunch of side-activities, like making friends and buying property - as in, these things can only be unlocked once you've gone far enough in the game, which seems like a cheap attempt to force people to move along the main path.
The combat of Fable 3 is based on three approaches: "Strength" (melee), "Skill" (ranged), and "Will" (magic). This has been simplified from previous games. For one thing, your weapons are now automatically upgraded as you progress through the game. There are some non-standard weapons, but these require large amounts of investment to upgrade (one gun has "kill 500 undead" as an upgrade qualification, when it's possible to only kill roughly that many enemies of all different kinds across the entire game). The only neat feature of the weapons is that your "main" weapons change shape based on how you progress in the game; hidden achievements will shape your weapon's appearance, such as a bone handle for killing the undead or a pearly one for using the "shock" spell frequently.
Magic has been simplified, as well. In Fable 1, there was a "mana"-style limitation on how many spells you could cast. In Fable 2, this was removed in favor of charging times to cast different spells. In Fable 3, spells like "slow time" and "summon creature" have been made into potions, and the only spells that can be cast are direct attack spells like fireball or lightning bolt. This simplification was clearly intended to make the game flow better, but instead it just makes it so there's really no drama to any battle - you just do the same thing, over and over, for a hundred different battles.
One thing that Fable 3 attempted was to get rid of the heads-up display almost entirely. Health is no longer measured, but regenerates after a while - the only indication of its existence is the fact that as you get hit the screen gets a little bit redder. The "emote wheel" of previous games has been dropped; instead, you interact with people and use a predetermined "nice" or "mean" emote. Oddly, the first "nice" option is always dancing - even though this is for a complete stranger, and there's a perfectly serviceable "shake hands" option that doesn't show up until you've already done a few other actions. In addition, for someone to go from an "acquaintance" to a "friend", you have to do an annoying little fetch quest for them - and you'll have to do this for everyone you want to make into a friend, which means that apart from getting you more "guild seals" it's barely worth it.
The main menu has been replaced, too, with an in-game location: the sanctuary. This is probably the most obvious and annoying change, as rather than simply pausing the game to look at your inventory, status, and so on, you have to literally teleport to a different location, which sort of messes up any sense of continuity when you can be in the middle of a fight, hit start, and be instantly teleported to your safe-house to change clothes and weapons. One very important aspect of this is that there is no longer a map that you can use without teleporting back to your sanctuary - and the map in the sanctuary is basically only usable for buying property in towns, which means there's no "actual" map of the various wilderness areas you have to travel through.
As mentioned, the actual draw of Fable - the ability to do things other than the main quest - has been played down, in a way. You can't do a bunch of things until you unlock the ability to do so by going through the main quest, and the world itself is pretty boring and drab. There's a few attempts to make different towns and locales, unlike in Fable 2 (there's an industrial town, a gypsy-like town, a hippie commune, and so on), but it's all pretty dull. You can get married (heterosexually or homosexually), but the interactions are so shallow that it's even less worth it than it was in previous games. The one potentially-neat thing about the game is the cooperative gameplay, which is far more fleshed out than in Fable 2. In Fable 3, not only can you have another hero in your game, but heroes can get married and even have kids (or adopt). Still, cooperative play is usually good to begin with, so this isn't really in Fable 3's favor, per se.
Overall, Fable 3 is a disappointment. There are a lot of places where it seems like they could have actually done something good, but the need to simplify and streamline everything held both the story and the gameplay back. It doesn't feel like there's that much content - interaction is boring, combat is boring, and the actual development of your character isn't that much of a big deal. Overall, Fable 3 gets a 4/10; the production values are decent (if a bit buggy), but in terms of inspiration it's a pretty bad game.