hedwards: I think you misunderstood. Platforming in 3D doesn't work, or at least I haven't seen any games where it has worked out. I think the closest I've seen was the AC series, but it's stretching the definition of platformer way too far.
There may be games where it works in 3D, but I haven't yet played one. Even Gexx, which is an awesome game, fails in terms of controls compared with the 2D platformers.
crazy_dave: Ah I see what you mean. Isn't Psychonauts a 3D platformer? I've not played it myself, but it gets high marks.
It is, I own it and in general I do like it, but the controls get rather awkward at times and it's quite difficult sometimes to hit the marks you need in order to progress.
I may have mispoken, it's not that they can't do it, it's just that it isn't really the right format for a platformer and is quite difficult to execute properly. Give too much leeway and it feels like autoaim, give too little and you get something like Epic Mickey which is completely unplayable. I literally was unable to make a jump to get out of that first room, and I tried for longer than I care to admit.