I for one am excited about the prospect of playing Captain Marvel. He has been sorely underrepresented in video games up to now. Refreshing.
And in terms of him being a Superman knock-off: If you know anything about comic book history, then you know virtually all superheroes are in essence Superman knock-offs. He was the meaningful first.
If you look at Captain Marvel's history, relationships, and source for his powers, you can see he is quite different from Supes.
And yeah, in reference to Sentry, I always hated the character. I find him too bland.