Akichi Daikashima said:
A:JJ is incapable of transferring any feelings into any of his movies, even Super 8, where the opportunity to prove himself as a director was glaring right before him, and Half-life isn't so old that it needs modernization; the story has a unique vibe to it that when removed, would make the story rather bland and uninteresting, leaving only the unique gameplay, and as we all know, gameplay is the hardest thing to transfer onto cinema.
B:THAT could work, but again, you'd need to keep consistent with the theme, otherwise it's a spinoff, and the only "good" vg-movies that worked with that kind of approach were the Resident Evil movies, but they work because of their slightly schlocky/bad movie feel.
To quote Yahtzee:
"A game(in this case movie, but I believe that it still applies) that fails due to over-ambition is still better than a game that fails because its beep-boop committee designed sludge coughed out by a corporation staffed by robots(in this case J.J. Abrams)"
To counter your points:
A: Wasn't Super 8 a nostalgic tribute to old Speilberg movies like E.T.? (I never watched it, so I'm going off of what I remember from Movie Bob's review) So wouldn't it be pretty likely that because of his feelings from the past he fumbled while trying to emulate it? I don't know, I could be wrong about that.
B: Well, if either of these movies (portal or half-life) were to be made, they would most CERTAINLY need to focus on something that barely touches the original story of the games. For portal I would like to see an Sci-fi action movie about Aperture's collapse at the hands of GlaDOS. For half-life, however, I don't know of any approach they could make.
Either way, the movies should NOT be about anything having to do with the main stories of either game. The best videogame movies always seem to be far removed from any plot in the games.
Also, on a tangentially related topic: What if the portal movie was an interactive puzzle where the entire audience had to cooperate to finish each puzzle? That would be an interesting experiment.