Honestly, I didn't find Seyfried likeable, I think it's more that there are just a larger number of vocal Cosette fans around because there are more fans. I didn't see much about her performance that was particularly endearing.
I do take the point about the lack of solo lines not helping Les Amis in the movie, but I think Combeferre and Courfeyrac, plus Joly, had more character than usual in the movie thanks to the differences between the media of stage and screen, and some of the things they added (like the stuff with Gavroche). I say "they" in terms of filmmakers, but tbh I feel like Killian was just doing his thing in the background half the time considering a lot of his great little lines weren't in the script. But I'm probably being ignorant about film there!
Revolution: like Christmas come early only with more death
"Les Amis Fun Package - The Awesome Traits of Each"
"She's basically Enjolras meets Amy Pond"
Sings Stars "way better than Russel Crowe"