Never thought he was a good quarterback. He was only "good" his rookie year because it was his first year and teams didn't know his tendencies or anything. Now that they know he's greatly regressed. I don't think he can read defenses well at all, hence all his scrambling, and he's not a very accurate passer. Two basic things you need a QB he is well below average in, imo.
You compare Cousins with RG3, and imo, Cousins is the much better qb. He just hasn't had his chance, because he's not an "exciting" player like RG3 and doesn't have the media appeal that RG3 has.
This could be like what happened in Philly once Vick went down. Foles played out of his mind and earned the starting job, I really think Cousins can do the same. Sure Vick was/is on the backend of his career, but RG3 and Vick are basically the same player, except Vick reads defenses better.