Um Lex was pretty damn serious about killing Superman. I mean while not as good as teh Machiavellan Lex, I don't think I've seen a more viscious attack on Supes and cruel by Lex than the one Singer shot in SR, though it was meant to be rimancient of the Passion of the Christ, so for better or worse in that regard it was made so.
But his anger htere is blinding. And yes, I found having watched it twice on DVD that besides the amazing plane sequence a lot of it just doesn't have much replay value and you lose interest. But whenever Kevin Spacey is on screen you perk up and pay attention. He is charismatic and magnetic like Lex should be. He is funny and sardonic throughout and he and Parker Posey are very fun to watch together but starting with when he is threatening Lois Lane's son with kryptonite until the end he becomes the most evil bastard in a GOOD comic book movie in a long time (Magneto, Doc Ock, Ra's, etc. even GG to an extent were made sympathetic).
P.S. While I miss the Machavellian Lex and would love to see him, I'd take Spacey's scene stealing performance over Smallville's botched poor man's version of Harry Osborn though.