The picture on the new cgi versions is better than it has ever looked and the effects very much match the original work without all the dirt from the optical comps/ effects that back then you had a picture that was 3rd generation on the opticals versus the shot footage of the actors which was first generation.
Unlike lucas paramount never saved the opticals so they could not re-composit them with digital computer technology they way they did the star wars special editions.
The new computer effects are similar in nature to the director's edition shots done for robert wise's star trek I, that they look like something that could've been achieved the time the shows were made.
I am very surprised they did not update the effects because Enterprise happened before kirk and co and looks more futureristic.