Disclaimer: I play exclusively on huge maps on epic speed. So all commentary are based on that.
To me, it feels like there are two difference paces at work.
The first is the meta-game (how you win). This seems very slow (and mostly about right). By turn 150, I've got an idea of what's going on, how I want to proceed, etc.
The second though is the day-to-day game (what you're doing from turn to turn). And here, the game is -very- fast. In one of my current games, by turn 125, I'm fully expanded (barring war) at 4 cities who have nothing left to build (spamming buildings aside). By comparison, on a huge map at marathon speed in Civ 5, this 'nothing to do but hit end turn' stage doesn't hit (for excessive periods of time) doesn't hit until within a few hundred turns to the end of the game. As well, by turn 125 in such a game, I've generally barely gotten started serious expansion; generally, I'm still at 1 city and working to make it mostly profitable in some fashion.
The result with these two dramatically different pacings is that you quickly ramp up in the early game and them rapidly plateau to how the game will be settled in the end-game. Any sense of mid-game (and thus uncertainty) is gone very quickly.