If you mean you think you could only go to Kanto in Crystal, you could go to Kanto in any of the other games.
They wouldn't add all of the regions to one game, though, for the obvious fact that it would take up far too much space. That would be a pretty nice idea for a proper console version of Pokemon (a world tour game of sorts, where you could bounce across all of the regions; a console game has ample space to allow that), but it won't happen on the handhelds.
Still, I want them to keep Kanto. And even though I rarely participated, the bug catching contest would be pretty nice, since it gave an early-game stab at Scyther/Pinsir.