If Spike is considered "lamer" as he becomes, progressively, informant, reluctant ally, comrade-in-arms, hero, and finally, Champion, couldn't we say pretty much the same thing about Angelus, once he became Angel? (Calm down, Bangels, I'm not attacking your hero, only trying to make a point)
The villain is, if portrayed properly, almost always more interesting than the hero, simply because he is more mysterious, more sinister, and just plain more fun to watch. Batman in downright boring compared to the Joker. Superman has a superhero sized stick up up his Kryptonian a**, but Lex Luthor is downright fascinating. The cowboy hero rescues the rancher's daughter simply because he IS the cowboy hero. Black Bart, on the other hand, has specific reasons for wanting to force the rancher to sign over the deed to his ranch, and without those reasons, the cowboy hero might just as well ride on back into the sunset.
Those who consider Spike's progressive evolution from Big Bad to Champion as increasing lame-ness do have something of a point in the fact that, once Spike decides to impress and become closer to Buffy, that becomes arguably his single motivation for the rest of the show. No more plotting to kill the Slayer and take over Sunnydale. No more Gem of Amara. No more alliance with a cyborg super soldier. All we have is a vampire with romantic interests in a Slayer, and that's just about his entire motivation through to the end of the series. That, to some people is considered "lame."
Speaking only for myself, I see more to Spike than that one simple motivation, mainly because I made the decision to look for, find, and appreciate the more subtle changes in the character, his interaction with Buffy, Willow, Xander, and the others. I like the way that James portrayed him, the way that he slowly evolved from "Saturday night is when I kill you," to, "You're THE ONE, Buffy." I see things new and interesting in Spike in every episode that he appeared in. He wasn't always admirable, but, as contradictory as this might seem, there was usually something to admire about his character, whether it was his loyalty and genuine love for Drusilla, his growing friendship with "happy meal on legs" Joyce, or his genuine affection and sense of protectiveness for Dawn. He made a promise to a lady, and he kept it. Every night, he saved that self same lady, even though it didn't matter anymore. In order to atone for the attempt of an unspeakable crime, ha did something that, as fer as we know, had never been done, or even attempted by another of his kind. He stood beside his Slayer against an entire army of "vampires that vampires fear," and was instrumental in their destruction at, as far as he knew at the time, the cost of his very life, and he laughed while doing it. He was the first to volunteer to stand beside a man who he had every right to despise, to face yet another army, to fight in another battle that would almost certainly be suicidal. And let's not forget, he just might be instrumental in helping save the world yet again in the next few months.
I call all of that pretty impressive for such a lame character. Course, that's just one man's opinion, but I like to think that it's pretty valid, arrived at honestly and logically.
