I don't want to answer for Chris, but I'd rank them something like this:
Dark Souls >= Dark Souls 2 > Demon's Souls.
From a mechanics perspective, I think Dark Souls 2 is easily the best in the series and that smooth frame rate really makes a big difference. However, I don't think that Drangleic is quite as interesting as Lordran was. The lack of shortcuts really bugged me - you're always on a march to the next bonfire, rather than exploring the environment to create shortcuts between areas.
Also, there are a lot of parts of Dark Souls II that feel like they're engineered to be annoying. It's like they made them harder just to say that the game is even more unforgiving. There's no real reason that certain bonfires need to be as far as they are from certain bosses, or that certain bonfires already have enemies in attacking distance.
All that said, I still really loved the game and definitely plan to go through New Game + after I finish up the Dark Souls 1 DLC. You shouldn't be too scared of this one. It's got a tough opening, but once you get over the hump, it's a real breeze.