I recently got my boyfriend into Fullmetal Alchemist, so I'm watching that, too! We're watching the first one because I think that the relationship between the two brothers is more compelling.
In the past we've watched quite a few, like Cowboy Bebop, Higurashi No Naku Koro Ni, Get Backers, Kinos Journey, Chobits, and Death Note. I've tried to get him into the longer ones like HunterXHunter and D Gray May, but he doesn't seem to have the patience.
If anyone knows anything that's 'relationship' based (where you actually care about the characters)/not too long/not 'just another' highschool anime... Message me! We're almost done with FMA, and will need a new one soon.