Last week it was number two; the week before that it was nothing, because it had just been released. Social City, the new city building game from Playdom, has flown to the top of our weekly AppData list of top Facebook gainers by daily active users, adding more new players than games several times its size.

There’s obviously some heavy advertising from Playdom behind the scenes. But as we found when it was brand-new, Social City is actually a great game. Nevermind that players have experienced technical problems since the game’s launch; they keep coming back anyway.

Proof is in the numbers. We’ve been watching Social City’s DAU as a percentage of monthly active users — the number of people among all the players who return daily — for several days. Following the launch-time spike of new DAU, Social City’s percentage settled to its current 44 percent. Defying our expectations, it hasn’t dipped any further. It’s an extremely high number that seems to show Social City’s new players genuinely love the game.

Nevertheless, Playdom still has to fight it out with other publishers to rule the emerging city building genre. At lower positions below, you can see two similar games, Towner and My City Life:

	Name	DAU	Gain	Gain, %
1.	Social City	2,475,502	+1,732,288	+69.98
2.	Birthday Cards	2,636,459	+1,333,714	+50.59
3.	FarmVille	30,973,370	+1,060,995	+3.43
4.	Café World	8,896,906	+366,051	+4.11
5.	Texas HoldEm Poker	6,637,643	+332,075	+5.00
6.	Mafia Wars	6,552,404	+201,596	+3.08
7.	Tiki Resort	590,285	+192,160	+32.55
8.	Pet Society	4,456,973	+152,818	+3.43
9.	Bubble Island	580,362	+150,714	+25.97
10.	MindJolt Games	3,329,168	+144,263	+4.33
11.	Bejeweled Blitz	2,798,882	+87,439	+3.12
12.	Towner	189,978	+77,490	+40.79
13.	Mahjongg Dimensions	228,713	+63,324	+27.69
14.	2010 Bracket Challenge	54,335	+49,459	+91.03
15.	PoxNora	46,975	+46,507	+99.00
16.	Country Life	2,577,705	+46,329	+1.80
17.	My City Life	532,022	+38,604	+7.26
18.	Games	279,840	+38,579	+13.79
19.	Bola	87,397	+37,532	+42.94
20.	SPP Ranch!	200,026	+34,773	+17.38

Following Birthday Cards, which is only loosely a game, there’s a foursome of Zynga games: FarmVille, Café World, Texas HoldEm Poker and Mafia Wars. All said, Zynga has managed to add about a million DAU since last month, edging over 67 million this week.

Tiki Resort returns us to Playdom. This island resort building game was released a couple weeks before Social City, but it only has about half the players and far fewer DAU. Still, if you’re not measuring it against its sibling’s stand out growth, Tiki Resort is doing pretty well.

One special circumstance to note this week: every one of the top 10 games on the list is from a large or well-funded company. That’s not the case every week, but it may happen more often as the big boys acquire ever more leverage to promote their products.