And 9 times out 10 that's why you get crappy CG, because the director or producers think that since it's all done by computers it's as simple as pushing a button and *POOF* instant top notch, completely photo real CG. It's really no different with practical effects, you try to go cheap and you'll get crappy effects that look like something from the old Buck Rogers movies from the '20s or something out of an old Godzilla movie.
Yet, The crappy effects add to the nostalgia of the old Sci-Fi series and movies. Poor CGI is only a distraction.
But I am biased. I'll take the original Godzilla movies over the remakes any day.
Even better if I still had my little Hitachi TV.
Today's poor CGI is tomorrow's kitschy nostalgia.
To me, what matters more is keeping the overall feel of the work intact. So, yeah, the stop-motion of the car full o' Nazis going off the cliff in Raiders set against a matte painting? That looks totally cheesy, but I accept it as part of the work as a whole, and in keeping with what was available in the time period.
Flash Gordon serials I can appreciate, wobbly sets and all, because they were working within a budget, and it's true to the feel of the rest of the show.
I recently got my wife in to Star Trek: TOS. I have it on blu-ray, with the option to turn on the new f/x or leave the old ones. We went with the old f/x because so much else about the show just says "1960s." The lighting and framing in various shots, the stunt work in the stage fighting, the acting styles, the writing, all of it just screams "1960s." It would be, to my eyes, way more jarring to have all of that going on and then suddenly cut away to a perfectly modern-looking CGI render of the Enterprise. It's the same reason that a lot of the updated f/x shots in the Star Wars OT don't feel right to me. I mean, ok, make R2 blue. Fine. No big deal there. But doing some "cool" CGI flyby of an X-wing during the trench run? No thanks. Maybe as a novelty, but give me the option to turn that off and go back to the old models (which, I should add, were incredibly well done).