It's true I didn't really take into account the "elemental" relationship of light vs. electricity

. And technically, as hyper_megaman said, electron base velocity is about 1/10th the speed of light. However, when excited with photons, electrons can gain energy and increase in velocity/momentum. So in effect, Kizaru's ability will be amplifying Enel's ability (at least in speed).
The difference is that light aka photons are pure energy (supposedly with no mass/momentum) but electricity is charged particles (ideally electrons) with an electrical potential and mass/momentum. However, we saw by Kizaru's own words, that "speed is weight" so he can put momentum behind his light speed which takes away any physical advantage Enel may have over Kizaru. As far as electromagnetism goes, it cannot affect light. From what has been observed, only gravity affects light (gravitational lensing etc.)
If I had to guess though, I'd say that the relationship between Light and Lightning is the same as Cloud/Smoke and Flame... light can be a product of lightning the same way smoke can be a product of flames. So it's a draw as far as element vs element goes.
Though a bit off-topic I wanted to explain the situation between Ace and Akainu too. There was a good physical reason why magma was greater than flame. Basically flame requires air (as a fuel in a chemical reaction) to burn whereas magma is a semi-fluid/solid form of packed heat. So by snuffing out the air that burns the flame, Akainu's magma was able to burn Ace's body through conduction of heat.