I don't think those two screenshots are a very fair comparison. Broken Sword 4 isn't going for a cartoony look. (And I personally think the facial expressions on BS4's characters are awesome.)
Cassius Pearl is one game that seems to be pulling off a crazy cartoon world in 3D quite well.
As far as the "it must be 3D" philosophy, Telltale has a lot of reasons for doing graphics in 3D (and I'm sure many other developers have the same reasons) - it's faster and cheaper (allowing smaller companies to make games for less money, with fewer resources), it's much easier to edit camera angles and animations on the fly (which allows for a shorter development cycle), and it's a must for a downloadable game. It would be impossible to keep the file size so small with 2D graphics.
I personally don't mind 3D graphics at all, and I don't really get why people are so passionate about them. I like 2D or 2.5D (which is what the Runaway screenshot above is - those may be prerendered backgrounds, but the models are 3D) but I like 3D just as much if it's done well. And keep in mind that 2D graphics can be ugly and poorly done, too!