Highlander.
I am aware it is apparently being remade, but that remake will suck a massive dick and you all know it. Highlander deserves a REAL remake.
Highlander is an example of a fantastic concept executed appallingly. This was a film about immortal warriors, duelling through time, over centuries, gradually gathering to one location so that one of them can stand tall and take the ultimate prize. It's so. Fucking. Badass.
And the film is dogshit. I mean, it's entertaining, sweet in places, kind of awesome at moments, 'I'm in disguise,' etc. But it could have been so, so, so much better.
In fact one rumour I heard about the new one was even a pretty good idea, that being that one of the immortals might have been using a shotgun to blow people's heads of instead of cutting them off. That's awesome, and could lead to an amazing action scene.