All of the Reeve's Superman movies need this. The effects, while amazing at the time, are super dated. That said, probably not enough bucks involved to do it. Thing has to sell, and I'm not sure a revamp of these movies will do it. And they're classics, things of their eras, especially the first one. Really don't want to spoil it in my opinion. It's still pretty amazing. That entire helicopter scene...

So I'm in the pen of 'leave them alone', mostly. George wanted to polish his Star Wars nest eggs, because control freak, and could, so he did. That of all movies, Star Trek: The Motion Picture got not one but TWO Director's Editions, both making more VFX shots, the latter in 4k(!) among other changes (sounds, cuts/adds of scenes/dialog) is just astounding to me. That one. Two special cuts. How and whut. Star Trek Fans are Powerful Indeed? shrugs All I know is I was and am here for it, that movie's kinda special to me.

OOH. The Black Hole. That one could use your sprucing up, that's for sure. Love that stupid movie RIGHT UP to the end parts. Little slow, but hey, not bad for a first shot at a Sci Fi Live Action movie from Disney, and some of those effects still hold up! Just need to come up with another ending... I get the idea, but c'mon.

Anyway. Most movies can probably use a bit of sprucin'. But unless it has a way to be monetized, it's just not going to happen. And in the case of your HP example, it's just not enough bang for any bucks sent along. I would be surprised if enough HP fans would actually buy HP8 just for the few minutes we're talking about.

I say leave them alone... with grand exceptions because there's always exceptions. BvS and ZSJL come to mind. Similar to TMP, studio screwin' with it (different reasons of course) and the edits that were supposed to be in the theaters (as far as I'm concerned) wind up being much better. Well, to me anyway, there's quite a few who will still disagree, and that's fine, but that Snyder got to get the 'right ones he meant to make' out is still a good thing, you ask me.

Edit: just thought of TRON. Man. That one could use some vfx editing help for sure.

Edit2: Aw, man. The Last Starfighter. Could you imagine?