Okay... yes we know that Buffy never truely loved spike but there was something there from time to time even though Buffy denied herself... she'd been there before, fell in love with a vampire and he'd inturn lost his sould and killed or tried to kill a number of people close to her... lets remember the relationship evolved after she was brought back from the dead... they were both dead things... she was dead inside, ripped from heaven while spike was and is a vampire... blah blah blah
As for Riley? After Parker what else was there, he was rebound guy... down to earth, a gentleman unlike any other man she'd met before, that is until she found out his sordid little secret... 😛
But Angel... her first and probably will ever be her only love, they fought side by side to save the world, she took his life not only to save him but to save the world... remember she's cookie dough, until she knows what she wants she'll never be ready and if Angel is still waiting outside that oven when she's all baked and full of cookie goodness... the who knows 🙂
ANd he's FORTY?!?!