Forsaken? More like Forsucken, from what I've heard.

That game has the general reputation of being pretty bad among members of the Descent community. I've never had the opportunity to play it myself, but from what I know of it, it's nowhere near the level of a Descent game.
Aldo, FS2's reviews were one thing I forgot to mention about the whole "FS2 killed WC" debate. As far as I know, FS2 received marks in the high 90s pretty much across the board; every old review I've read was positively gushing. To the best of my knowledge, the WC games didn't reach that level.
Regarding the presence of other 6DOF games, there really isn't anything else out there, with the possible exception of Forsaken, that has Descent's style of gameplay. Corridor-based isn't really much of a factor, since D3 featured outdoor environments as well. The exact mechanic I'm talking about is a full six degrees of motion, with the ability to hover and place, completely unaffected by gravity. There really isn't anything else like that out there. As for "having done it all" with the Descent series, how can you then justify the absolute flood of groundpounder games out there that are almost exactly like one another? There's absolutely no innovation in that genre; pretty much anything that came after Quake has been close to a carbon copy with different environments/weapons. There may have been a few tweaks along the way, but the core gameplay is still exactly the same. Against all of those games, we 6DOF fans have the 3 Descent games. Kinda one-sided, isn't it?

And, even if you're confining Descent to a 6DOF corridor shooter, there's still a lot of gameplay mechanics that have never been tried out, as the Core Decision team is currently working on.
P.S. Ever hear of the game NTrap? It was a planned 6DOF game with a fantastic physics engine and the ability to construct and lay "traps" for other players. It also represented the best hope in the Descent community for a Descent mod. Sadly, that project fell through. Right now, what little hope we have left is pegged on the people at HighOctane Software who are working on Core Decision.
Just feel very, very fortunate that the Freespace community has FS2's source code and such an active, vibrant modding community; Descent's modding and level-building community is all but dead. We're a group in dire need of new blood.
A.K.A. Mongoose, for you HLP denizens