Big stars are a good bet for good movies because of their acting abilities. Take Bruce Willis, Morgan Freeman, Brendan Fraser and Kirk Russel for example. The plot is also very important and not the same ol horseshit over and over like zombies and vampires.
I’d rank it genre->actors->[knowing the original story if there is one]->trailer->director->reviews
That goes for both actors I like (say, Marc Ruffalo, or Scarlett Johansson) and ones I don’t like (Meryl Streep, Mark Wahlberg)
More than they should be. There are sequels I’ve skipped in part because they didn’t have the original cast. Getting a top-drawer actor secures more money for better effects and promotion. There are movies like “Vibes” and “The Shadow” that sank beneath the waves because they cheaped out on SPFX, and they did this because they couldn’t attract A-listers to the cast. In that sense, actors are pretty important. (When “The Shadow” was released, I think Penelope Ann Miller was actually a bigger name than Alec Baldwin.)
My daughter is an actor. So, pretty important.
Bradley Cooper, as a voice for a gross fox, is highly preferable to seeing him act live or poorly attempt to sing live. The remake of A Star Is Born is only a decent remake if it’s aired and produced by Nickelodeon. If he’s in it, he has to be a cameo or side character. Same goes for Denzel Washington who has never learned to speak differently than his own voice. Accents are as foreign to him as Americans are to vegimite.
On the plus side, if Michael Caine is in it, or perhaps Michael McKean, it’s on the watch list.
And it does matter in certain cases: ie: I love Batman. But Baldwin??
I mostly don’t care - some I enjoy seeing when they’re given roles that I think fit their personality and/or general appearance, but a given actor or actress won’t usually be a draw for me if the rest of the movie seems like shit.
OTOH there *are *some that I intensely dislike for no good reason and I can’t help but hate whoever they’re playing. Don’t ask me why, for example, I want to tell Tahmoh Penikett to SHUT UP AND GO AWAY whenever he’s on screen. I just can’t stand the fucking sight of him. I don’t know why.
I’m not meaning to pick on Two Many Cats, but this comment seems to be a common theme in this thread - that people don’t have much respect for acting skills in contemporary actors. I think that’s really harsh - I think there’s some incredible actors around, ones that make or break a scene. Olivia Colman, Helen Mirren, Nicole Kidman to name the first ones just off the top of my head.
There may be plenty of average ones about - but let’s face it, most films are shit action movies aimed at 14 year old boys anyway. But some actors really know their craft, and I think it’s pretty daft to dismiss the whole profession so lightly.
and a lot prettier. 
I don’t really know who actors are these days, aside from the ones I got to know when I was younger and cared about those sorts of things. Directors, though, I will tend to follow.
The movies I enjoy are enjoyable for the cast playing great parts, but the acting is just part of the whole package. I’ve never went out of my way to see a movie just because a certain actor/actress is in it.
Perhaps they can act as well as you describe. Maybe it is a problem with the writing rather than the acting. I agree that the endless river of superhero crap makes it worse, but the writing in today’s movies is substandard too, for the most part.
Not only the stars are important, the supporting actors plays a big role in a good movie. There are actors who’s there for supporting roles.
actress at the most importance to me.
Some actors movies I’ll see, but story is more important. Some actors I will definitely avoid watching if they are in it. Meryl Streep as noted by others (who actually likes her?). Woody Allen, Kristen Stewart, and many others that I only think about when I see their names on the description before deciding not to watch whatever they might be in.
Same here, there are very few male actors I would recognise although I will admit I used to avoid Nicholas Cage until I saw “Knowing” and have watched several since - unfortunately, like Michael Cane, he always plays himself.
I will watch and actively seek out anything with Jennifer Lawrence in it, since seeing her with Craig Ferguson, then The Hunger Games.
Also watched Game Of Thrones purely foe Emelia Clark after seeing her in an interview.
Anything with Lena Heady in, since The Sarah Connor Chronicles.
Kiera Knightly - surprised me in Domino, had no idea who she was.
Probably some kind of perversion as similarly, I listen almost exclusively to female musicians/singers.
Never been a deliberate choice to exclude males, just grew like that.