In reply to The Lemming:
I think there's a big difference between records that were crucially influential in themselves and ones that are landmark records but were basically symptomatic of a bigger thing that was going on anyway.
The latter group would probably include stuff like Rapper's Delight.
The former would include stuff like:
Oh Carolina (classic Prince Buster, first JA record to feature Nyabinghi drumming, pretty much single handedly responsible for the later development of ska, rocksteady and reggae):
Under Me Sleng Teng (first all-digital dancehall tune):
Phuture - Acid Trax (er, yeah, acid / 303):
Alex Reece - Pulp Fiction (pretty much single-handedly killed off choppy breakbeaty stuff in a lot of drum and bass):
at least within their scenes...