why would anyone want a serious Bowser? Even in the 3D platformers, which are the closest Bowser has ever gotten to being "serious" (except SMG) he usually has some silly objective like Peach's cake (unless you interpret it the perverted way...)
Funny Bowser FTW. I really can't take Bowser serious anyways; if Nintendo wants to make a serious Mario villain, it should be a new villain, not Bowser. Mario has always been lighthearted as a series; I don't see the appeal of making one of the main characters dark and serious.
I don't think everyone's looking for a 'serious' Bowser, per say, but one that at least has a set goal and doesn't intentionally help his own arch nemesis. That's why I enjoy the BiS Bowser. He was out for revenge against both Fawful and the Mario Bros. and he still managed to be very funny.