Anyone who did not thoroughly enjoy the first Deus Ex game and marvel at it's different gameplay types should be taken outside and flogged!
This was the mould maker for an entire genre and while some others have come close Deus Ex has never ever really been surpassed (the second game was just rubbish). But perhaps that will change with the (hopefully) imminent release of Deus Ex: Human revolution.
Here's something to read up on http://en.wikipedia.org/wiki/Deus_Ex:_Human_Revolution