Dating back to the early stages of rock, there were many influences to modern day music. First check out Ivan's new lesson, "The Shadows Style Solo Lesson", and then post a reply to the following question. Who do you think had the biggest impact on todays instrumental rock music?

Directly - Steve Vai
Indirectly - Hendrix

I'm not that of an expert for those musicians, but Hank Marvin style proved to be very influential for both instrumental and with-vocals bands. For example if you hear Mark Knopfler or David Gilmour, you'll hear a lot of Hank Marvin in there. Also, Hendrix set some standards in the late 60ties that stuck for a long time. He influenced many many players to play in a similar fashion, including instrumental song composers.
When we go towards the present, in the 80ties there were a lot of different stuff going on. Influential music figure was also Miles Davis, who was becoming a star and creating various styles of Jazz, making instrumentals out of this world during 70ties, 80ties and even 90ties. Satriani also made a very influential "surfing with the alien" album full of great hit instrumentals in the late 80ties, and lots of people followed his style too. Steve Vai formed his style and released some hits that quickly established him as one of the leaders in rock instrumental genre.