Yeah I gotta say, one very underrated aspect of KISS is Gene's bass playing in the early years. Not so much in the '80s (partly because most of the bass on the 80s albums was played by Paul, Bruce and Jean Beauvior), but on the early Kiss albums, Gene's bass lines are almost genious and completely drive the songs. Awesome bass writing. Songs like Goin' Blind, Strutter, Love Gun, Detroit Rock City, 100,000 Years, hell most of the early Kiss songs - awesome bass lines!
Also I think its fair to say that Kiss by *far* had the biggest impact on inventing 80s "hair metal". Obviously bands like Alice Cooper, Van Halen, New York Dolls, Aerosmith and AC/DC had a massive influence too and hair metal kinda grew out of a mix of all that put together, but KISS was really the blueprint for it and had it all from the start - big stageshows, heavy makep, big hair, spandex & leather, theatrics, 3 minute sleaze anthems with big choruses, the fist in the air singalongs, big "air guitar" riffs, also one of the first hard rock bands to move away from a blues influenced sound & format (and have much more straight to the point songwriting with Beatles style chord progressions), etc. Where the other 70s bands who influenced the hair metal scene may have had a couple of the elements of hair metal each (which created when you put them all together), Kiss had pretty much all of them.