Aside from Star Trek, which is a gem on its own, I must admit that when I first thought of Shatner I thought that perhaps a pharmacologic intervention might be in order.
And then I watched him come forward on comedy venues like "Just For Laughs" and in a sincere and unselfconscious fashion, be utterly hilarious. Or watched him be everything I believe lawyers to TRULY be on Boston Legal (admittedly, not my favourite show!), and he was brilliantly deserving of his kudos.
And THEN, I heard Christopher Plummer interviewed and part of his response on an issue described how brilliantly Shatner was on the Stratford (Ontario, Canada) stage in understudy for Plummer, and that he knew then Shatner would be a star. And Christopher Plummer is arguably one of the best actors EVER! So he should know.
Bottom line: Shatner is a gem, and all the shinier because he can laugh at himself, is fearless in his artistic offerings, and more talented than he is given credit for.