I always thought this was pretty much a straight hack em up but I just noticed that 'RPG' is listed as a genré type on the game page - is this thing more like a Blade of Darkness/Die by the Sword type of thing or a crazy action RPG like Fable?
Cheers!

*edit* OK checking on Mobygames, I'd have to go with 'Action RPG'
BTW, coo - look at the box art for the PS2, bit better than the one GOG's using:
http://www.mobygames.com/game/forgotten-realms-demon-stone/cover-art/gameCoverId,86576/

This is currently on my play list. The games most similar to it would IMO be oldschool brawlers like Final Fight or Streets of Rage. You'll be doing a lot of dancing about lining up safe attacks and you can't proceed to the next section until all enemies in the area have been defeated. As far as I can tell, the RPG elements go no further than purchasing moves and weapons/ armor in between levels.

I think it's pretty fun but it might not be the kind of game you're looking for. I'd youtube some gameplay footage of it. I would also strongly recommend a gamepad as there is no camera control.

they will slap "rpg"on anything nowadays =/
but i think the "rpg" tag come more from it being a d&d game