Honestly, by the time I saw Dooku use the lightning I wasn’t at all fazed because I’d used it myself in however many video games. If you need someone to blame for lightning not being unique to the Emperor, blame Kyle Katarn.
EDIT: Holy shit, there’s five pages of this?! Sorry if this is no longer relevant, it was on the page where I clicked “reply”.
No, you’re definitely correct. Force lightning was devalued by video games long before AOTC… but the more I think about it, the more it annoys me that the Emperor uses what had come to be regarded as a pretty basic Sith ability.