Remakes are best when they're done of bad old movies. Ocean's Eleven is a great example. The original was crap, but the remake was great, though the sequels to the remake are a mixed bag.
I don't really like to see someone remaking a film who's trying to making it darker, edgier, sexier, faster, etc. It seems like lots of remakes are only attempting to update special effects, social norms, and cash in on a younger audience, who'll see the movie because it's got actors they know, while trying to rope in people who liked the original. And when you try to be all things to all people you're probably going to fail which is why it's better to remake something already bad to give yourself a better chance.