I am looking at getting one of the d&d games. Which is the best? Do the need to be bought in order?
You can't go wrong - they're all pretty close to each other in fun/theme/playability (as evidenced by the poll results.) I'd give the slightest of edges to LoD due to the more interesting hero powers and the fact that the dungeon tiles are a little more closed off (ie., you tend to get dungeons with more walls and directionality and fewer large open areas.)
But they're all good.