I never understood Bangel fans calling Riley boring because imo Angel isn't that much more interesting during his time on Buffy.
Yes Angel has a much richer background with Angelus, Darla, Drusilla and the curse. But a lot of what makes him interesting gets explored on his own show. On Buffy he's mostly the mysterious guy who gives Buffy information, makes out with her or is someone she has to worry about.
Angelus is obviously great, but that's also when Angel isn't Angel.
I think him trying to help Faith in "Consequences" is one of the first times Angel himself becomes interesting. He understands what it's like to do horrible things and have to live with them, which basically becomes the premise of his spinoff.
I'm not saying Riley is some amazing character either. I just always thought him being the All-American guy was kind of the point. He was supposed to be the anti-Angel. Normal, dependable and someone Buffy could have a relationship with without all the supernatural drama. I just don't think Marc Blucas played that type of character particularly well.
I don't hate Riley and I'm not saying Buffy should've ended up with him. I'm Team Cookie Dough Buffy.
I just think Angel benefited massively from getting his own show and developing an identity outside of being Buffy's boyfriend. Riley never got that opportunity.