Robb Stark
King in the North
I was thinking about why Riley didn't really work with Buffy, and I think "IWRY" was the epitome of it. It was hard enough to get into Riley after everything Buffy and Angel had done and gone through in the first three seasons of the show, but then Buffy goes down to L.A. and we basically find out that her and Angel truly are in love with each other. Even if you don't like the Buffy/Angel pairing, that pretty much slays any momentum Riley had going (and there wasn't much to begin with). If you were into Buffy/Angel (and I was so into it), it made it pretty much impossible to get into Riley.
It didn't hurt Spike because he didn't get into Buffy until a full season or so later (and because Spike is one of the best characters ever), but with Riley it was just flat out rejectionville after that.
It didn't hurt Spike because he didn't get into Buffy until a full season or so later (and because Spike is one of the best characters ever), but with Riley it was just flat out rejectionville after that.