Not as bad as you might first think. Although the original movie is a classic, Michael Rennie didn't exactly knock the scenery down with his emoting in the original role, either. I think Reeves could pull it off quite well.

The gag line you imagine is almost irresistable, and I would be disappointed if there wasn't an outtake to that effect on the eventual DVD.

I would love to see Gort done almost the same, except with the enhanced, wrinkle-free possibilities of computer animation thrown in.

Few people remember that in the original story, "Farewell to the Master," the punch line was that the robot was the dominant species, not just a super cop. While the incorruptible robot police/army idea is certainly attractive, eventually it would result in the robots becoming the dominant species. The classic SF story "With Folded Hands" was a cautionary tale in this vein, and in the later stories based in Asimov's robot universe, intelligent robots were already starting to view the Three Laws as a "living document."