When you finish a game, you can see your rank by going to...well, rank. The highest I've gotten is fourth place, I think. Winston Churchill is the number one leader. What does it take to beat him out? Has anyone done it?
You'd have to be on diety or emperor (I think higher difficulty gives you extra points), you have to have A LOT of cities, each with A LOT of population, make sure you have plenty of the wonders, discovered most if not all of the artifacts, have a high culture output from each city, and make sure that each city has a high output of gold or science, whichever it is you have it on, make sure you have a lot of great people, make sure your borders are high, you're people have to be sophisticated, and learn all techs. Future Technology gives you bonus points.
I've only gotten above Churchill twice, and both times I was losing until the late game and then I came back and won Domination victories (Deity Level). I don't know if the come from behind victory gives more points, but every other game I win where I am leading from start to finish I usually end up #3 or 4 in rank.
I once got 1st place on Emperor by preforming a Conquest as Germany. Maybe it helped my score that all of the other civs were eliminated? Maybe it was because I had over double the techs that the last civ had
I just recently did the same with aztecs on deity. When I had conquered everybody with artillery and tanks, all other civs still had pikemen and archers and legions. In other words my tech was overwhelmingly advanced. I took over all cities for fun before I deleted the last capital. I won in 1800s. I did not end up on top of the ranks.
To win on top of the ranks you have to be close to winning on all conditions and you need to do it very late in the game to have cities that have basically all buildings and improvements. I think I played this game better than any earlier win on deity or lower difficulties when I've won in ~2050 and just a few turns away winning on all dimensions.
It is a power/size game to be top of the ranks and not a rating on how well you played the game.
OH, and by the way, what version do you have, it might effect the scoring system. I play the DS
Regarding the rest of what you wrote, yes of course you need to play well to be strong, but I prefer nowadays (compared to earlier) to try to win as quick as possible along one strat rather than "just" building up my civ. AND a quick win in any of the dimensions is usually not rewarded in the scoring system. It is easier to get a good scoring when winning late in the game and with most things done.