I agree, I was kinda dissapointed too, that there was no reward. And no, being loyal to a video game character doesn't qualify as a reward

I mean it's no big deal obviously, but small things like, I don't know, Liara "moving in" in your cabin if you stayed faithful, would make the game much more personal and unique without much effort.
Unique is the important word here: it's just weird that the romance is the exact same regardless of your ME2 "activities". I really, really dont't want a ME space-opera with big jealousy scenes, just a small appreciation like the "moving in" would have been nice. This way it would feel much more like I'm playing "my" Shepard rather than some random dude.
A comparable situation is your spectre status. You either stay or become a spectre in ME3, which is fine. But again, the game would be much more individual and unique if I got some small reward for staying a spectre throughout ME2, like a spectre paint or an old spectre weapon. This, like the "moving in" is very easy to implement , but imo it would improve the feeling, that I'm actually playing my Shepard.