The nice thing about the old video game commercials that I've seen from the 80s and 90s is that they didn't try to decieve people about how the game itself looked; all attempts to make the game look cool/fancy were limited to maybe live actors acting out the game on Hollywood sets. Sony and EA set a bad example in video game marketing with this kind of crap.
The ads from the 80s and 90s led to me not having any idea what the Zelda games even LOOKED like ingame, never mind what they were about. Why would I buy a game when I have no idea what it's about?
Nintendo commercials, in the US at least, always showed gameplay. Sometimes they followed this sort of forumla:
Live action/real actors, weird stuff happens, gameplay footage, boxart (sometimes with system).
For instance SMB3 had all those people in colored shirts (live action/real actors) then the camera panned out to show they were standing in formation to create a giant mario that could be seen from space (weird stuff), then you'd see some gameplay followed by a shot of the box art possibly next to an NES.
Thats how i remember it anyway, but yeah Nintendo always shows gameplay so i don't know how you couldn't tell what the game was like.
I agree that PSX games were decieving way back when, you shoulda seen the look on my face when after always hearing that FF7 had better graphix than "all my n64 games combined" from my cousins and finally saw what the game (see: NOT the FMVs) really looked like.. Big ol' grin on my face :-D followed by laughter.