The opening sequence of "Superman Returns" shows Clark's ship going into what I have always assumed to be a wormhole...but it could have been something else.
Indeed, there is that possibility, but at the same time that may have just been a route that Superman discovered to speed up the time it takes travelling between Earth and Krypton.
Then again, perhaps the opening sequence was merely the Sol and Rao systems with a collection of random celestial phenomena filling the journey in between. The wormhole actually appears more like a black hole/gravitational anomaly, but who knows.
I love the Donner-verse movies, but I just couldn't accept the events depicted in those movies being written into Superman comic canon. It starts with Superman altering the rotation of Earth to turn back time (one of the lamest methods of time travel ever depicted in fiction), peaks with Zod and company using finger telekinesis and ends with Superman using "masonry vision" to rebuild the Great Wall of China.
The Donner-verse Superman gave Earth 1 Superman a run for his money in the powers department.