I liked Gravity! It did a decent enough job with *some* of the physics, and was enthralling enough as a story and a spectacle, that I was prepared to ignore the really obvious science failures and just enjoy it for the artistry, which was staggering.
I tend to avoid seeing films I think will be bad, so the worst one for me is Apocalypse Now. I saw the Director's Cut OMG Supreme Redux Delite Platinum Extra (you get the idea) edition on TV several years ago, and it was the single most tedious film I've ever seen. I'd rather watch Star Wars 1-3 back to back than watch Apocalypse Now again, and SW1-3 made me want to remove my eyes through my ears with a rusty crowbar.