Yeah, if you don't romance one of the original ME1 characters, you're basically out of luck for ME3. They at least added some stuff in the Citadel DLC for Jack and Miranda, if I remember right.
They did, but it feels half assed in comparison.
If you romanced Liara in 1, stayed faithful in 2, and rejoined her in 3 it was head and shoulders above any romance in the whole game. Every other romance was either for a single game, had speedbumps, or was basically ignored. Meanwhile Liara is treated as your sweetheart and your true love throughout the whole thing if you choose her. No other choice gets the same treatment. It's nuts.
(Don't get me wrong though. As a Liara fan I love the romance. I just hate that it was the only one that was good from start to finish. I would have killed for the same treatment towards Jack.)