It kind of seems wrong though to remove Wario only because he's had his own series and LOLWaluigi didn't.
I don't see why. Regardless of what Wario's done he's had a starring role as an anti-hero in 8 games and...well I'm not too sure what to call him in the six and a half Warioware games, but probably not villain as most of his actions are perfectly legal. Part of the criteria is if a character spent the majority of their time as a villain -OR- were more memorable as one; for Wario to count, one has to try proving that those 14 games are either a minority or less memorable than other appearances.
Waluigi at his worst is certainly better than Wario's worst (who, judging by the Wiki, tried DESTROYING A PLANET), but he doesn't have a giant stack of games against him.
EDIT: Also a playable anti-hero in Super Mario 64 DS, though I wouldn't call him a star. Baby Wario appears in Yoshi's Island DS as an anti-hero, but I'm not sure I'd count him the same as regular Wario or it as a starring role. Number of important non-villain roles could jump up to 16 if you include them though.
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In this world which will someday fall to ruin...
...dreams and hopes don't matter at all.