I agree. While a Wario series could be interesting, I don't think it would work if it only focused on Wario due to how he isn't that deep or likable. Plus, I always thought that he was suppose to be the anti-Mario kind of character.
I would personally prefer a Mario anime series, which would include all of his frienRAB and enemies in the cast, since I personally like Mario more than Wario. Still, if a Wario series was made, I think that it would also work best as a comedy more than action/adventure, but that's just me.