I dunno, Wario was in Mario Land 2. I thought he was just a cheesy add in like Tatanga, but then he starred in more games to come.
Waluigi's art looks official, and I think Camelot had Nintendo's permission or help. I think we'll be seeing this lanky fellow in a Super Smash Bros. sequel or the next Mario Kart. So keep those fingers cross-ed.
I'm a Pokemon fan, so what? Mario's still #1 in my book.