Eeeehhhh... excellent is probably going a bit too far. They're definitely good, solid games with generally pretty decent writing and mechanics, but they're not particularly... well, more than good. They're very consistently what you'd kinda' call second-tier RPGs, methinks. What you go to when you've played or can't afford most of the really impressive ones.
That said, particularly the newer ones (The Avernum remakes, Geneforge 4, 5, the Avadon ones to perhaps a lesser degree -- due to UI issues more than anything, as they're a lot more user friendly than the older ones) are definitely something I'd recommend. They are good, and particularly the geneforge and avernum series have some of the most interesting settings RPG computer games can offer, even if the mechanics and writing isn't really much more than just competent.
Don't want to downplay 'em too much, I think, and they're pretty damn impressive from the standpoint of how they've been developed, but also don't want someone to be approaching them expecting more than they are, basically. They're just good, and definitely worth the money when they're on sale (which is fairly often, eheh), but not amazing or anything.