The one thing Johnny and Lando have forgot to point out though is that Sunshine is able to suspend your belief. Yes it's only 50 years into the future, and yes from a scientific perspective, the concept of the film would be all but impossible. When I first heard of the movie, I thought it sounded absurd. But somehow, it all seems perfectly feasible when the movie actually starts. Sunshine is "high science fiction." More like Solaris than Armageddon.
28 Days Later may be a zombie movie, but from an artistic level, it runs far deeper than any other movie of a similar theme. The same goes for Sunshine to some extent.
The point is that Sunshine is an amazing, and dare I say, original science fiction movie for the first 2/3rds of the movie. Then it kind of digresses into typical science fiction fare.