...a much better singer than I am.
...a very good replacement for Axl Rose.
...most likely the next AI winner.
That's right. Not just Axl, he can cover Robert Plant, Steve Tyler, Mickey Thomas, and probably Freddie Mercury. If you examine the actual vocal qualities of Plant and Tyler cutting through the mix and going for the high notes, they don't have the most pleasant vocal qualities either. Whether he's to your taste or not, a rock vocalist with Lambert's range, control, and power doesn't come along too often. I count maybe 8 in the last 40 years (i.e., Plant, Tyler, Paul Rodgers, Mickey Thomas, Axl Rose, Bobby Kimball of Toto, Lou Gramm of Foreigner, and Freddie Mercury). Lambert could be one of them.
For a vocal interpreter, I like Danny Gokey and Kris Allen much better. Gokey can rock out at least as well as Huey Lewis but with more range. Kris is an excellent singer when in his zone and could be an excellent arranger/producer. But if you want somebody to rock out in front of a band, it would be Adam.
Edited to add:
Isn't Adam Lambert what GnR fans have been waiting for--an Axl Rose who shows up on time, sober?