Honestly, I’d say that Splinter Cell is considered to have had a larger impact on gaming than it really did. For example, you claim that Splinter Cell was the first game where lighting mattered - at the very least, Thief: The Dark Project featured that very prominently, four years earlier, but I doubt that was even the first.
Splinter Cell basically just copied Thief and Metal Gear Solid’s homework and changed it up a bit, I’d say it’s inferior to both games, and yet is often considered to be one of the best games ever made.