I kind of agree with neogaf posters that Dark Souls doesn't fit on our list
From Software's games trace their lineage to Ultima Underworld much more than anything like Castlevania. So if we have UW on the list, then Dark Souls belongs there too.
Saying it "doesn't fit" is just pandering to the retarded Codexers who feel like viewing UW, Arx Fatalis, Gothic or Witcher 2 as RPGs and Dark Souls as anything but.
I haven't played King's Field or Shadow Tower, so it's certainly possible that those harken back to Ultima Underworld and friends, but Dark Souls specifically just doesn't. It plays like what you'd expect from Castlevania if you made it 3D and reduced the gameplay to combat alone. Besides, if we look at its predecessor, Demon's Souls, we'll see a much more arcadey game, with worlds you can pick and stages you progress through in a very linear manner, each concluded with a bossfight.
Let me put this another way. One of the difficulties in defining what an RPG is comes from the fact that people enjoy RPGs for many different reasons. However, without getting into the everlasting definition debate, it's usually possible to cluster them into groups based on their features. So, for example, we can have a group of Ultima Underworlds, System Shocks, Arx Fatalis, etc, where some people obviously believe the shared feature set of these games qualifies them as RPGs. The thing with Dark Souls is that it's not really similar to anything else on the list. Hence, it doesn't fit.
And honestly, Bee, does it really upset you so much that some people don't consider DkS an RPG? Come on, it doesn't fucking matter. I've probably spent more time playing Dark Souls than you have, and it doesn't fucking matter to me, that's for sure. Like, I think Thief is better than most of our top10, and you can definitely see the Ultima Underworld/System Shock influence in it, but I don't consider it an RPG, and that is just fine.