I don't think I'd be too excited about a Half Life movie, it has the greater potential to end up just being another ho-hum shoot-em-up action film. I find these obtuse and boring.

A Portal movie, though.... I'd be all over that shit.
 
A Portal movie would be interesting in my opinion, something different from most of the stuff you see now days.

But a lot of these movies based off of video games seem to rarely happen, let alone get released. There's always some bullcrap that delays it for years or something that keeps it from happening.

Either way if a portal movie comes out I'll be sure to see it