My brothers bought me the box set for Xmas (thanks guys!), and we watched all the movies over the Xmas period. These flicks were the dog's bollocks when I was a teenager, and it's interesting to revisit them now I'm getting into my mid-thirties.
The first flick, lest anyone forget, introduces the idea that some undead monster can get you in your dreams. This, plus the concept of dream logic, forms the basis of the whole series.
The second is frankly a TV movie, with a mad flaming rampage at the pool party tacked on at the end.
Three really kicks off the visual inventiveness, has a ball with dream logic, extends the Freddy myth, advances the story in a logical fashion, and features spectacularly bad performances from Lagenkamp and Wasson. Note that this flick is interesting because all of the supporting characters are necessary to advance the story - they are (at least initially) a team, not random kids to be killed in cool new ways by Freddy.
Four again ups the ante on visuals while dampening down the horror aspect: This is the point where the supporting characters really become Freddy-fodder. I just love Freddy's resurrection, though (the dog pissing flames on his grave).
Five is piss-poor story wise, but there is some interesting stuff on dream logic (either that, or pages of the shooting script got mixed up...), and it is the most visually inventive of all. Not much horror left, and I believe it's this disc which carries the Freddy-Fat Boys rap as an extra. My God.
Six is piss-poor in every respect.
Seven I like because it's almost a dry-run for Scream. It's Craven's LA Takedown. But Lagenkamp is a fucking terrible actress.
All in all, the overriding impression is of diminishing returns in terms of horror content, but, as someone above pointed out, Robert Englund clearly has a fucking ball with his character.