Well, as Nathaniel said, love is easily the most common topic for songs, and that's what it is. A topic. It isn't a genre. There are love songs written in many different genres, and written in many different ways, so I don't really think it's possible to judge all songs that mention the most potent human emotion as one. For example; a love song can be about an innocent crush, (The Beatles - I Want To Hold Your Hand) or it could be an intense, unhealthy obsession, (The Police - Every Breath You Take). Those songs are nothing alike, other than there being some intense emotion present in both.
Well, I knew it wasn't a genre, that was just for the lack of better words. I'm well aware there are many styles, but in my opinion they still feel samey, dull and generic because of the topic. But I can't deny there are the occasional songs that I can forgive and enjoy. Maybe I'm not that big on love, I can't relate to it much and I just find the subject uninteresting, and there's nothing wrong with that.