So I guess Smallville is ending? Anyway, the Onion A.V. Club has a pretty great review of the
finale (there are spoilers on their site, but I won't quote any of them) that merges into a succinct summary of the whole show-recognizing, accurately, that Lex Luthor was always the star of the series:
"When Smallville was still new, a friend of mine who had been watching it for a while explained to me that it was this strange but compelling show about a likable, tormented, misunderstood rich boy and the suffering he was forced to endure because of his attempts to forge a friendship with a super-powered doughnut hole.
...
Rosenbaum is the only actor who's given flesh to this take on Lex: the rueful, heartbroken genius who, after realizing that he can't be either Clark's friend or his equal, settles on a life in which he's defined as his nemesis. Rosenbaum's Lex remains one of the great TV series performances of the past ten years, and proof once again that talent will blossom in the least expected places."