You get higher scores on maps with more people because if it's a military game you just took more cities, and even if you don't, larger maps let every person build more cities, more cities = more land and more population = higher score.
So yeah, Time will always be the lowest score because it'll be the latest. Space Race is usually pretty low too, though you can at least get Augustus with space if you wage a few wars and get pretty big, or rex like mad, or can pull off a very early space race.
Cultural is usually higher than space if you get it earlier, like in the 1800s or earlier, and all that culture will usually let you flip a few cities, adding to you score.
The highest are usually domination/conquest wins, and the earlier the higher the score. An AP diplo victory can get you pretty high score though, rivaling a domination victory because it can be accomplished so easily so early. Some of my 100k+ games were diplo victories accidentally won in the middle ages.