As I type, the IMDB has Gravity as #41 on the top 250 movies of all time. I'm in no position to disagree. It's way up there, anyway.
Unless you have been living in a cave for the past few weeks, you already pretty much know the premise: The setting is low earth orbit, and the (fictitious) shuttle Explorer is visiting the Hubble Space Telescope to install new equipment. Disaster strikes when a Russian satellite goes awry and unleashes a torrent of orbiting debris that slices and dices everything in its path, including the shuttle and Hubble. Leaving seasoned astronaut Matt Kowalski (George Clooney) and neophyte mission specialist Ryan Stone (Sandra Bullock) without a ride home, running low on O2.
President Obama would call this a "glitch".
Yes, the special effects are jaw-droppingly realistic. At some point I dropped my filters and simply accepted it: sure, they must have filmed this on location. [Quibble: I'm pretty sure the filmmakers' orbital mechanics are a tad unrealistic, but that doesn't show up on the screen.]
But you can only go so far with special effects. Clooney may be a fantastically rich pretty-boy actor in real life, but after a few seconds I was totally buying him as a right-stuff grizzled space veteran. Ms. Bullock is equally wonderful, managing convincingly to portray someone who's simultaneously terrified and resourceful. (And the movie gives her ample spots to be both.)
This movie and its makers should get how many Oscars? All of them. All four acting categories, even though there are only two actors. Even for animation, dammit. Cancel the ceremony and just issue them now.