It rather begs the question how fast Kal-El's rocket was travelling: in the film, Jor-El's holographic projection mentions that he has been dead for thousands of years, which is consistent with the idea that Krypton was very remote from earth.
The Superman movies clearly have Krypton be a ludicrous distance from the earth. The whole "dead for thousands of years" crack by Brando, the fictional galaxy name, and the fact that it took Superman - SUPERMAN - five years roundtrip get there and back.
I have not seen the Donner cut of II, but dollars to donuts there'll be even more references to distance.
The whole conversation in RETURNS that Superman has with Aunt May about how he's the sole survivor of Krypton seemed a little odd. More than one person has mentioned that it might be a set-up for a spin-off or Supergirl movie.
I always thought Supergirl's origin could do away with Argo City, which always seemed like an unecessary "middleman" in the origin; just have her rocket off in suspended animation (or in time dilating near-lightspeed) as an adult from Krypton. Which is what the recent writers did.
In the comics, of course, the trip to earth seems very short, a matter of days or even hours, which you couldn't do over a distance of 27 light years, if one supposes that the rocket can't travel faster than the speed of light. More likely, Kal passes through a wormhole at some point, which makes the distance academic. Maggin has Superman casually mention that he uses wormholes as shortcuts when travelling through space: they truly are a boon to science-fiction writers.
Funny you should say that, because E. Nelson Bridwell once explained that Kal-El's ship used a wormhole to travel to earth, and it is through this hole that chunks of Kryptonite were blasted to Earth. What's more, that's why Kryptonite keeps on showing up: because the wormhole linking Krypton to Earth stayed open. This also accounts for why so many other things from Krypton find their way to earth (e.g. Kru-El's weapon box) with some regularity.
It rather begs the question how fast Kal-El's rocket was travelling: in the film, Jor-El's holographic projection mentions that he has been dead for thousands of years, which is consistent with the idea that Krypton was very remote from earth. If the rocket was travelling at close to the speed of light (and one allows that Kryptonian technology was equal to such a feat), that would sort of make sense, what with relativity and all. It would still have taken Kal quite a long time to get here, though, and indeed he seems to age a few years during the trip: he departs as a baby, but seems to be about three when he crashes. Still, it's scientifically iffy.
This reminds me of an unintentionally hilarious Young Earth Creationist Wiki site that explained that the reason we have light coming from distant objects is because at some point in the distant past, God increased the speed of light. Young Earth Creationism and FUTURAMA collide!
I wish I had kept the link; it would be good to have a look at it before it became a wholly infiltrated parody site.