Because of the enormous success of Scott Snyder and Greg Capullo's New 52 run on Batman, most everyone sees the New 52 as a good creative move for Batman. I also happen to be a big Superman fan, and things for the Man of Steel have been more tumultuous. Grant Morrison kicked things off with a Golden Age-inspired run on Action Comics that ended up in Morrison-level multidimensional wackiness, we had a new take on Doomsday in "Doomed," a revolving door of writers on Superman, and we're now in the thick of a depowered, identity-exposed Superman in "Truth."
Superman Homepage reviews for all 47 issues of New 52 Superman and Action Comics and compare those ratings to the previous 47 issues of pre-New 52 Superman and Action Comics (94 + 94 = 188 total issues). These are the two flagship titles for the Man of Tomorrow and so make sense as a basis for a fair comparison.
The conventional wisdom is that Superman has been hurt by the New 52 move, but according to the ratings from long-time Superman fans themselves...
For pre-New 52, the average ratings on a 5-point scale were as follows:
- Superman -- 2.56 for story, 3.83 for art
- Action Comics -- 3.40 for story, 4.00 for art
For the New 52, the average ratings were higher with regard to story and comparable with regard to art:
- Superman -- 3.33 for story, 3.54 for art
- Action Comics -- 3.69 for story, 4.10 for art
So overall, even though Superman is often held up as one of the casualties of the New 52, the stories have actually gotten better in the 5 years of the New 52 compared to the 5 years pre-New 52. (Also important is that the standard deviation of the quality was lower for the New 52 stories. This means that the stories were pretty consistently 3's and 4's, whereas the pre-52 stories ranged widely from 1's to 5's but mostly 1's and 2's).
Of course, this isn't to say that the stories have been great or objectively "good" ... just that they've been better than the stories in the years immediately prior to the New 52 according to long-time Superman fans. I personally have liked a lot of the New 52 Superman stories. I was not a fan of John Romita Jr's art on Superman starting with issue #32, but I have actually liked "Truth" quite a bit more than I expected to. Hopefully whatever "Rebirth" turns out to be in 2016, it will be even better yet.