I had always thought the similarities between Bill and Ted(dy) were intentional considering the shows share a producer in Jim, uh, Dauterive. The latter is definitely less of a sad sack, though I suppose people's tolerance for his intense neediness varies.
As for Barney, he can be a bit of an unsung character. His role as Homer's closest friend was usurped by Lenny and Carl once they started appearing regularly in scenes at Moe's. He does have a lot of good one-off jokes in the classic era, though it's the case that the writers didn't want to continually wallow in his sad state of affairs, and yet also couldn't have his stint of sobriety last either.
