Geno is less important to Nintendo's gaming history? I don't know if that's entirely true...on what do you base that opinion? Wolf may have made an appearance in more games than Geno, but the game that featured Geno was released a year before Wolf's first game appearance (though if Star Fox 2 hadn't been canceled, he certainly would have appeared first). I'm not sure if that's even really the point though. I think it's more a matter of...if we were to remove both of them from their games, would the series then have been significantly different?
Removing Geno would have likely had little to no impact on the future of the Mario RPG series. However, Geno's role in Legend of the Seven Stars was fairly important, and the game came first in its series of related games. It's within reason to think that because the success of that game paved the way for future Mario RPG titles, it has a fair amount of historical significance.
Wolf, on the other hand, was a supporting character to the Star Fox series added in the second game. Do you feel the success of that game is as important to the continuation of the Star Fox series as was Legend of the Seven Stars to the Mario RPG series?
I think Wolf is a good character, and would be a good addition to Brawl. I just don't quite agree with (or perhaps understand) your previous statement.