You can't really judge the legs yet, because it's had to compete with an overperforming WWZ, and a slightly overperforming MU. I do think some people are being harsh on MOS, and I do think the numbers are misleading with what I've just said about above.
You could factor in and say Man of Steel overperformed in its opening weekend and is evening itself out. It was always going to be tough for it to make 50m this weekend, especially with WWZ making 66m (I mean, not many people expected that) and MU making 81.2m; that takes up 147.2m of the box office, which doesn't leave much to go around for any other big weekend numbers.