I would rate "Them" as one of the better, if not the best, of the "big bug" movies of the 50s, the Sci-Fi decade. For that era, the special effects in "Them" were pretty good.
Only those about my age would remember that movie. I remember the first time I saw it, on TV, way back then. Terrifying experience for a young boy.
Yes, I used to really enjoy vintage scifi, mostly books, and Them was probably one of the better made movies of its kind. At one point they were cranking out really bad B movies almost as fast as the SCIFI Channel did bad B movies in the 80s and 90s, and almost as poor of a quality. I don't think anyone really cared, I think a lot of those old films were made mostly for Drive-in theaters where people weren't really watching the screen anyway.
Nothing worse than a bad re-make of a bad B movie to start with. There are some exceptions though... Remember Kingdom of the Spiders from the 70's? Will Shatner? I think Spielberg's Arachnophobia was a copy (not legally proven, but, prolly so) but way better... one case where remake won out. Now as to remakes of remakes, like the remake of the remake of The Fly... that's another conversation.
Taken to ridiculous extremes, there's been a zillion Frankenstein remakes, and the best in my mind is still the one by Mel Brooks.