For the record, I do believe Narusegawa was canon, though the romance progression was virtually non-existent. ;^^ I also thought Love Hina was seriously annoying.
You'd be in for a surprise if you decided to watch Shuffle. I'm not entirely sure if it'll be what you're looking for, but this is the only harem I've ever felt content with watching and I do feel it's something that romance fans should strongly consider watching. That's not to say I don't like other harem anime (I actually think they're really fun), but this one has some really good closure. The level of ecchi is roughly the same as Haganai. Sorry it's not slice of life, but the fantasy setting does add a really nice touch to the atmosphere. It is also one of those anime that are a bit slow to start, but it'll be much more enticing in the later episodes. Trust me when I say it'll be worth it.