Elfin Lied. (Just kidding, but that series does has its moments...)
Macross Plus, and Full Metal Panic would be good choices. The first session of FMP is mostly the two of them in 15 minute episodes, but the second session actually has a real storyline that's really good.
I guess it depends on how romantic you need. I've never really jumped into anime like that. (In fact, I try to stay away from those.)
Rosalina: But you didn't.
Robert: But I DON'T.
Rosalina: You sure that's right?
Robert: I was going to HAVE told you they'd come?
Rosalina: No.
Robert: The subjunctive?
Rosalina: That's not the subjunctive.
Robert: I don't think the syntax has been invented yet.
Rosalina: It would have had to have had been.
Robert: Had to have...had...been? That can't be right.