Firstly, the essential knowledge about the Sony Mastered in 4K Blu-ray series is that it still has the horizontal resolution of 1920 (i.e. 2K) only, not 3840 (i.e. 4K). The 4K refers to the master, not the Blu-ray. It gets rid of all features in order to get the highest bitrate for slightly more video details, i.e. similar to Superbit DVD. So we get slightly improved video quality over the previous Blu-ray releases. The color is also slightly better because of the use of xvYCC extended color gamut. (An exception to the slight improvement is Ghostbusters – the Mastered in 4K version significantly improved the video quality from the previous version.)
Spider-Man 2 (2004) had been the best superhero movie before The Dark Knight (2008) was released. However slight the video improvement may be, I love improved video. I just want to mention a major disappointment I have with the Spider-Man 2 (2004) Mastered in 4K Blu-ray – it lacks the 8 really important minutes from the extended cut, also known as Spider-Man 2.1. So, don’t throw away the old version yet.
(The same thing happens with Total Recall (2012) Mastered in 4K Blu-ray – it is the theatrical cut instead of the Extended Director’s Cut.)