What game do you find compelling that uses 3D on mobile, and that its design depends on 3D and could not be done with 2D?
Have you actually seen the latest games for the latest smartphones/tablets?
Yes, but I have not seen any 3D game that makes me want to really play it. I find the 3D aspect interesting professionally, and from a technological perspective, but I don't find it adding entertainment value.
Yes I'm a 2D fan myself, I really like 2D platform games and adventure games and don't think 3D adds anything to it, but when I have to create a new game the customers expect 3D these days,
I disagree that customers demand 3D on mobile. In fact, I disagree that they demand it on desktop, for many game concepts. Despite what my personal tastes say about it, tons of people play stuff from casual vendors such as Big Fish Games especially from the "Hidden Object" category.
Does 3D add significant value and (more importantly) improved visuals to puzzle games, to hidden objects? Do you think people wouldn't play Torchlight if it were 2D? 3D games we already very strong back in 2000, yet Diablo II was mostly 2D.
I don't think people's tastes are all that radically different today. Games can be improved by 3D, but it might be unimportant, and it may significantly hinder the visuals of the games if they have the same budget. A game with 2D sprites, background et al can take advantage of excellent renderers in 3D modeling packages and only then be touched up in Photoshop to improve the look. A game with 3D environment has to have great texture artists, great modelers, great shader writers and display the entire good looking 3D environment quickly on even poor machines.
It all depends on what your market is.
so it's very nice if you have an engine that works on all platforms and you don't have to change your workflow constantly.
I agree with this one completely!
It does depend, however, on how complex is it to implement your ideas with an off-the-shelf game engine, and sometimes it may even be so with an off-the-shelf renderer. Just sayin'. :-)