I didn't expect to love it that much either but everything was on point OMG. The story, the characters, the plot twist around the end, the soundtrack, the photography, etc etc...
Also it annoys me when people act as if I wasn't a ~real sci-fi fan because I don't think that Star Wars is like, the best thing ever... I mean I don't hate it, it's just that I like anticipation better than space opera, so there's a lot of sci-fi movies that I rate above the Star Wars franchise.
It took me forever to watch Star Wars because I just never had any interest in it because it wasn't how I liked my sci-fi. When I finally caved my friends were horrified by my indifference. I mean I like it well enough, but its by no means the best, it is just one of the more easily palatable.
Minority Report and Gattaca are what attracted me into sci-fi as a kid... Moon is one of my faves in this decade's sci-fi films. I'm not a huge fan of the Aliens franchise. But weird enough, I loved Prometheus.
Alien / Aliens
Gattaca
Sunshine
Moon
Minority Report
The story, the characters, the plot twist around the end, the soundtrack, the photography, etc etc...
Flawless movie.
It's just a personal preference.