How do you define good theatre?

A continuation from: http://www.theatre.asn.au/poll/what_faqs_would_you_like_adde "How should we define 'good', and what qualities should a good show have?" Logos notes: "If we are still talking about helping Directors produce "good" theatre then are we not discussing a hugely subjective issue. I have been to see shows which I considered absolute rubbish that received standing ovations and seen shows I loved that played to 4 or 5 people a night and got panned by reviewers. There are a number of threads on this site that attest to this. Quite passionate attacks on shows and defence of same. I am reminded of Paris and of course Rock Apocalypse. "So what constitutes good theatre? Many people seem to believe that for amateur shows, particularly those with a lot of young people in them, effort from the cast and overcoming obstacles are enough to consider a show good theatre. I don't. "Theatre needs to entertain, I feel that very strongly but then we must consider what it has to say. If it only entertains and has no message are we doing the right thing by Thespis. Oh and by the way, it is important that the cast understands what the show has to say. If they don't the message will fail." Additionally, some people in the business say that good theatre must have a 'message', whether it be political, social or of other important topics of the day. Personally, I find shows are 'good', when the production has strong, believable characters, few mistakes, a clear and defined script, and the design aspects enhance the performance subtly. I prefer a performance which takes me down the road of the unexpected, rather than the retreading old ground (what I call 'domestic' plays: that is, if the play is something that can be seen anywhere and anytime in the world, and does not bring something new to the themes or storyline involved). This is from an audience point of view... so perhaps we need to split the question into two parts. What makes a good show from the audience's POV, and what makes it good from a cast/crew POV?