Power Grid has a lot of simple arithmetic. You're adding numbers in your head constantly. Barring a runaway leader, the endgame tends to have a slingshot effect where the person who is "leading" is actually behind those who are currently in 2nd or 3rd place. Timing this come-from-behind win is a big part of the fun for me.
It's the #6 game on BoardGameGeek [1], and well deserved to be there. Saying that "it's filled with math" doesn't make it sound all that exciting, but there's a good spacial element, an auction system that gets quite tense at times, and opportunity for "screw you" behavior that actually pays off. The winner is typically the one who was most efficient and has made some clever plays to keep his opponents out of his chosen markets.