I heard this one the other day, and I'm surprised it hasn't been posted yet. Those with a keen synth ear will notice there is more than one version of this out there, the original 1983 version and the 1989 version. The original had a slow attack on the synth lead, which to me is one of the features that memorializes the riff. Perhaps not enough people had access to the 1983 version because it made a resurgence with the 1989 version (which was actually a lot more popular). The '89 version of the song has noticeably more prominent attack on the intro lead, with what sounds like a bit of distortion on the open of the envelope. I haven't researched the actual synths each were made with or the rationale behind the change -- but maybe it would be an interesting discussion for this thread. Intuitively and from an un-researched standpoint, it seems to me the punch on the intro lead was designed to add a percussive feel to the lead, making people want to "move to it" more (i.e. a club mix). It could be that the latter version was made with a different synth (definitely sounds more digital to me).
The original (slow attack) version of the song is the one I remember best and consider iconic, though I think younger ears that heard them out of chronological order might prefer the newer, more digital (IMHO) sounding version.
The 1983 version:
https://www.youtube.com/watch?v=28Minfq_L2k
The 1989 version:
https://www.youtube.com/watch?v=jCHE0Tjw6MA