It was made by someone with attention to detail. When Cooper looks out the window, it looks exactly like the real footage of Apollo astronauts looking out the CM window.
The music is great. That can't be understated. The organ music lends a gravitas that's missing in other scifi movies.
But most importantly, it goes to the core of what I want from science fiction: it changed my world view, permanently.
Remember Doctor Mann, and his desperation to return to Earth? No other piece of fiction has made me feel that way. That utter, unspeakable, unbearable isolation of being the only human on this side of the universe. To be so far from everything that it's hard to wrap your brain around it. And if you do... you experience a Lovecraftian horror that drives you mad.
That's why I like Interstaller. It's proper, classic science fiction!