“Critically Acclaimed” = Critic speak for: “I’m casting pearls before swine. You’d have to be a boor not to appreciate this movie, but since you probably are one, you can still impress your friends by pretending to understand/enjoy this flick.”
“Two Thumbs Up” = Critic speak for: “It’s swill, but it’s good swill. Enjoy, you tasteless pig.”
I think you’ve got your answer right there. Admittedly, this is likely to refer to slightly more “highbrow” critics or those from the more highbrow media, but, when boiled right down, that’s all it does mean. But it sounds so very much better than being called “Sensation!!!” or “Smash hit!!!” or whatever by the Cretins’ Daily Chronicle.
Of course, months or years later, the same critics may have altered their opinions, but it will have worked as a marketing tool in the meantime.
Well, FWIW, my personal yardstick is that any movie that’s called “Critically Acclaimed” is probably going to be a serious art film that may be the best movie I’ve seen in years, but more likely is going to be a rather talky, slightly pretentious art film that I find myself slogging through just to make sure I’m not missing something. If I see it at the video store and it says “critically acclaimed” on the box, I usually wait until it’s off the New Releases shelf and is over on the Dollar rack.