Unfortunately thats how Nextgen currently works - backwards.
For some reason the image Description field (which can be long and contain html) is used as the Alt and Title value in the href and img statements. It does this in several pieces of code.
It should (in my view) use the images Alt/Title field (which is usually short and cannot contain html) instead.
Your lucky, my descriptions are huge with html tables so the effect on my site was much much worse (nb. it also clutters up your page source).
I display galleries on my site using [nggallery id=nnn template=caption] and had to customise .../view/gallery-caption.php so took the opportunity to style the output a bit. eg http://japaneseartsgallery.com/gallery/woodblock-prints/toshi-yoshida/. Previously if you hovered over a thumbnail you would have seen a html table displayed.
I live in hope that one day enough people will notice this and Alex will change all the code.