I think the days of over-budget, over-blown trailers are almost behind us. After all, Square used to be the kings of that kind of thing.
Remember this not-at-all waste of resources? Yeah, we know it's a tech demo now but 4 years ago we were convinced that was going to be something. I think a bigger problem this generation is fake demos like what Ubisoft like to do; things like Assassin's Creed Unity and, Aliens: Colonial Marines which are infamous examples. Another problem area would be Alpha, Beta and, Pre-Alpha footage since that kind of thing can be changed pretty drastically between when we get those first trailers and when the game launches.
There's one more, very new issue that just came about not too long ago and it's the P.T. style demo. I liked P.T. and Allison Road looked decent too. Our newest flavor of these things came with Biohazard: Resident Evil VII and before E3 had even ended, we heard that what was in the demo would be completely absent from RE7 itself. Since we don't know anything about Resi-7 yet, the demo (which seemed great) might as well have been called anything but Resident Evil 7. I can't wait until 2018 or 2019 when we see the release of early Resident Evil 7 game builds where it is just a straight-up followup to Resi-6! Hopefully that's not what we get.
TL;DR - When I see a pre-rendered trailer for an upcoming game, especially if it's an announcement trailer, I see that as confirmation that company A is working on game A and nothing more. It's hard to trust gameplay trailers too unless it's a game that another region of the planet already has widely available to its public. I'll trust a Yokai Watch 2 or Shin Megami Tensei pound-sign FE gameplay trailer before I trust the Dishonored 2, Breath of the Wild or, Resi 7 trailers even though I want those to be true.