To be honest, I find that his plays are very hit or miss. I really, really enjoyed Macbeth and Julius Caesar; they are engaging and interesting, and their characters are deep and three dimensional. On the other hand, plays such as A Midsummer Night's Dream and The Tempest (especially The Tempest) don't seem to me to be very interesting, and are driven primarily by flat, boring characters. Not exactly the hallmarks of good plays. Of course, this is just my impression of them; a lot of people seemed to like A Midsummer Night's Dream when we did it in class.
The problem I have with Shakespeare is his lack of stage direction and scene description, compared to, say, George Bernard Shaw, (who wrote Pygmalion, a play I feel is genuinely better than many of Shakespeare's, and certainly more worthy of study than some of them) for example. My teacher tried to shrug off this lack of stage direction by saying that it would be unnecessary, because we can tell what the characters are doing based on what they are saying, and while I acknowledge that there is some merit to that argument, it speaks more of laziness to me than anything else. It also leaves character interpretation more open than in a play in which every action is in the script, which is fine if you want to take the play in a different direction when you're putting it off, but it makes it impossible to study effectively, as far as I'm concerned. If Shakespeare had choreographed his plays more specifically, I would probably find them more tolerable (and the ones I like, I would enjoy more) because it would be easier to tell what, exactly, is going on. They're his characters and his ideas, and as such it shouldn't be on the audience to figure out what's going on.
So, uh... Yeah. He wrote some good plays, he wrote some awful plays, and he could have put some more stage directions in.