I say it depends on how much you want to understand the story. I am sure there are going to be a lot of references and hints at how stuff started that lead to the first game Deus Ex. But I don't think it will be necessary in order to get the main story.
Deus Ex is one of those games that you should just play purely as a game lover if you never did, assuming you can stomach the graphics :). I think they should remake the first title and resell it after this and update it ofcourse a bit to today's standards. It was a good game with a great story and tons of options.
As far as the second game stay away from it like it has the plague, they basically take everything out of that game that made it great :(.