Knights of the Old Republic and its sequel KotOR2 are action-RPGs (emphasis on RPG in this case) with a moral continuum like Fable's. If you liked being able to choose good or evil in Fable, you'll probably like choosing light side or dark side in KotOR. However, it's not as action-oriented as Fable. Don't get me wrong, you'll kill plenty of things - but in KotOR, you just give your characters commands and watch them carry them out, though you can move them in battle with WASD. It's not clicking once for each attack - full action- like in fable. Also you can only choose your character's face from a few options - other than that, appearance can't really be customized, though some armors look pretty nifty.
I doubt either game would cost more than $20.
Vampire: The Masquerade Bloodlines is an awesome action-RPG set in modern day. Appearance-wise, you can't do much to your character, but there are a TON of different ways to spend experience - you can increase your skill at hacking, your combat abilities, your ability to persuade people, etc. It shouldn't cost more than $20 and you can get it off Steam. (Google Valve's Steam if you're not familiar with it.)
IMNSHO, KotOR is vastly superior to Fable, as is its sequel. VTMB can be a little tricky to get to run smoothly, but if you patch it up you shouldn't run into much trouble. It's got flaws in terms of programming, but it's full of awesome, well-developed characters, great settings, and a really absorbing atmosphere.
Yea, I liked Fable, as well as both KOTOR and KOTOR2. (KOTOR2 was missing a LOT of content, and a few fans are making an awesome mod to include all the leftouts, so you might want to wait a few months until that comes out.) These aren't as Action-packed as Fable, they're sort of like diet Cola.
If you like the morale system, Lionhead also made Black & White. It's very slow-paced compared to Fable, but you can watch your creature turn into a vicious animal or a cuddly one, as well as fat or thin.
I heard somebody recommend Jade Empire, but I'm not sure if it's any good or not.
Yea I had both KOTORs and Jade Empire on my old Xbox. Jade Empire was a very good game. I remember the music in that game really standing out. Its a lot like the KOTOR games and you get to pick different options that lead your character to be good or evil but I do remember the story was although good, somewhat short like Fable's is which disappointed me but otherwise I did play through Jade Empire 3 or 4 times entirely.