Regarding Stadler's last two posts (because I don't want gigantic quote blocks):
Chuck's point was that Plant sucks/sucked live, and he took issue with your assertion "that this is not accurate" because his point was entirely subjective. Whether or not he sucked/sucks live is, of course, a very different question than whether or not he is "one of the greatest rock vocalists." Chuck is right that it's a subjective opinion that isn't susceptible of being accurate or inaccurate, but I agree with you that whether or not he is "one of the greatest rock vocalists" is more of an objective question (although not completely so). Your point seems to be that saying Plant "sucks" live is unfair if it is based on only his ~12 years of live performances with Zeppelin and doesn't take into account the last 38 years of work, and that's a well-taken point.
As for Plant's role with Zeppelin, based on what I've read, Zeppelin "was" Page and Jones because they were the two established players, and Plant and Bonham were unknown 20-year old kids. Once the band became established, however, Zeppelin "was" (at least as far as the general public was concerned) Plant and Page and, to a lesser extent, Bonham. Jonesy was largely pushed into the background (both willingly and by necessity). Behind the scenes, the band was, of course, Page's baby (until the post-Presence period when Jones took a larger role). To say that, since the mid-80s, Zeppelin is "Plant's band" is a bit of a silly statement because the band hasn't truly existed in nearly 40 years. Thus, that statement is really nothing more than an observation that Zeppelin cannot truly be Zeppelin (solely for the purpose of the small handful of concerts that have happened in the post-Bonham years and a few other odd public events) without its frontman. In other words, Page could never get away with performing as "Led Zeppelin" without Plant. As far as who runs "Led Zeppelin, Inc." behind the scenes...beats me.