Big news this week, as social gaming kingpin Zynga's Roller Coaster Kingdom is knocked out of the long-term top 10 Facebook games chart by new fish in town FishVille, also by Zynga.

This time last week, FishVille was lurking just outside the top 10 with 12 million monthly active users accumulated since being released into the wild on November 8. Now, it's added a further 8 million to that already impressive base and, in a numerologically pleasing development, has bubbled up to No. 8.

The only other placing change in the top 10 is that of Texas HoldEm Poker swapping places with YoVille - both owned by Zynga - and the developers will take heart from Texas HoldEm cementing its position, as rivals Playfish are stepping up to the table with their own poker game, Poker Rivals, backed with fresh investment from their new owners at gaming giant Electronic Arts.

Released just this last week on November 23, the number of active Poker Rivals players appears to be doubling every 24hrs. If it can keep up that formidable rate of growth then it'll be knocking on the top 10's door this time next week.

The Facebook games with the most active users from the past four weeks on November 27 at 14:00 GMT are:

1. FarmVille by Zynga (67,811,115)
2. Café World by Zynga (30,105,454)
3. Happy Aquarium by CrowdStar (27,331,512)
4. Mafia Wars by Zynga (26,919,961)
5. Pet Society by Playfish (21,722,878)
6. Texas HoldEm Poker by Zynga (19,666,142)
7. YoVille by Zynga (19,379,132)
8. FishVille by Zynga (18,749,742)
9. Farm Town by Slashkey (18,308,714)
10. Restaurant City by Playfish (17,400,293)

Numbers in brackets relate to total monthly users.