Young Sherlock Holmes is much more Spielberg-esque than the other movies he produced in the `80s. Poltergiest still had some Tobe Hooper elements like the parents smoking pot and the mom practically getting raped when the ghosts attacked at the end. Gremlins is 99.9% Joe Dante. His quirky humor is throughout that entire film. Spielberg's only real influence was Gizmo. The Goonies had Spielberg-influence in the action scenes, there's even reports that he directed those, but everything else was Richard Donner. Back to the Future had almost nothing to do with Spielberg. I think he was just producer-in-name-only on that franchise. But, Young Sherlock Holmes doesn't seem like it was directed by Levison. Watch his other movies and then compare it to this. They're complete opposites. And, yet, it has every single Spielberg trademark - including a William-esque score. Like I said, I'm surprised the DGA didn't do an investigation.
I always thought there was a bit of Spielbergian flavour in Gremlins, but only maybe on a surface level, the way it opens with the big Christmas song, that always struck me as Spielbergian, or maybe that is just because his name comes up at that point in the movie 'SS presents...' and i am hallucinating, lol.
Maybe it is just because it concerns families and a small town, and has the supernatural, and Spielberg has a lot like that, I shouldn't attribute those characteristics to him all the time though.
perhaps the constant in the two, Gremlins and YSH, is screenwriter Chris Columbus, his original take on Gremlins was supposed to be much more cuddley and quirky , rather than what Dante eventually did with it.
Also, I would say that Gremlins 2 was 100% Dante, and actually, in that light, come to think of it, i do think there is a Spielberg influence on the first one, Dante in fact demanded complete control of the second one or else he would not do it, so it ended up a self-referencing, post-modern wotsit of a satire. so that suggets Spielberg was in there with some decisions with the first one, making it retain commercial trappings, that the mayhem was contained within.
The Goonies i have not seen in about 20yrs so can't comment, but it did strike me as having some Spielberg in there, and again, like Gremlins, i think he probably did have some creative input at the meetings, shortround is in there, and it does have that 'kids on an Indiana Jones treasure hunt' vibe to it.
Poltergeist, we all know, defo has that SS flavour to it, it's like an 'R'/18 ET, and reports were that both had a hand in directing it.
I have not seen the second Transformers movie, but SS did not produce that one, and perhaps it suffered because of that, because the first one again has a bit of him in there, the kid discovering the alien etc, does have an ET vibe to it. I doubt he only brings along the doughnuts to the production meetings, the guy will have a say, and good ideas, and some of them in get in there, and i think that would have happened with Gremlins, although i guess there are some things he would not have put in there if it were totally up to him, and Dante had to push for them.
edit: and as for my earlier comments on lesser talents, don't get me wrong, I don't think SS was the best, just that he had the biggest impact of the late 70s/80s of any film director, just as i think there were better bands than the Beatles. His career has been fairly consistent, he still makes good movies(CMIYC, Munich), unlike Dante, whose Small Soldiers was basically an inferior re-heat of Gremlins, except now with a 'PG' tag, and the wildness tamed.
Levinson made Rain Man, which is sublime, but i can't recall what other movies he made, i know he directed the pilot ep of Oz, which was genius, but he defo followed the chords and riffs of SS on YSH, as you say. and he moved into producing afaik, so was not too confident about his directing skills i guess.
Donner is very hit and miss too, a great Superman, Lethal Weapon was good, but then you get stuff like Timeline, which could have been so much better, and conspiracy Theory, whioch was enjoyable, but a bit goofy and sloppy.