For me, ME1 romances were ok, but maybe even more so because it was the first time I've seen something like that. But when I replayed it later, the dialogue was a bit awkward and moved very fast. I mean, I felt like I had to push both Liara and Kaidan the fk away, because they started arguing about Shepard like they own her, even though I thought I was just being nice (definitely not trying to be flirty, because I thought it tacky for a boss to come on to her crew). And COME ON, the tacky "I could never lose you! *swoon*" in front of the whole crew after Virmire decision?? You're an *******, Shep.
Imo, ME2 romances were a bit campy ("I want you Thane." "I'm more interested in just *cough*TALKING~~wink~winkwink~ for a bit.") & they've really dropped the ball on some of them in ME3. I thought ME3 in general was ok, but to get the most complete experience, you'd have to romance (and like) Liara (which I did, so yay for me), she definitely gets the most content (largely due to Shadow Broker, because it ties all the parts in the series nicely).
In conclusion, I think ME did better with each new part in the series, but the one thing that ruined ME3 romances for me was that dreadful autodialogue, when you can't see the character you're talking to, so it lost something in immersion. (also, more choices in dialogue trees would be nice, like proper separate paragon and renegade routes to romance someone, as with Kaidan).