In degeneration i remember senator davis getting mad at claire when she made a suggestion about how to get out of the place. and he says "When did the NGO member become such an authority on the subject?!" and Leon replies "Shes one of the rare survivors of racoon city, she has more experience with this hellish nightmare than anyone here." But hes wrong, right? He has the same amount of experience as well.

Well, I believe that he was referring to everyone but himself. He simply left his name out, so as not to stray further from the subject than needed.

Leon just seems like the type of guy who would be like "Well... Some of us. Because I was the one who got shot, AND carried around that 10 inch Desert Eagle!!"

That's altruism, I think.

selflessness?

He was simply referencing her knowing more about the situation than any of them, not including himself since it was already established to everyone that Leon was an authority on the subject. So no one was questioning Leon's role, but, Claire's came into question. So Leon was simply stating "She knows more about this than any of you ever will. So believe me, she's more than qualified, so shut up and listen to her."

Well, we can be technical here for a moment, but until Degeneration was released, Claire did in fact have the most experience dealing with viral outbreaks. She lived through Raccoon City with Leon and then went on to survive Rockfort Island and Antarctica. Leon had only survived Raccoon City and then gone through the Las Plagas incident, but the latter wasn't a viral incident.

Of course, Operation Javier changes all that, but that was released after Degeneration. When Degeneration was out, Chris and Jill had survived three viral incidents, Claire two, but Leon only one.