Outlook for next month based on TrueAchievement numbers:
Happy Wars: 4049 owners - 3 days since release - BIG (free)
Worms Revolution: 290 owners - 5 days since release - slow
Naughty Bear Panic in Paradise: 152 owners - 5 days since release - very slow
Nights into Dreams: 517 owners - 10 days since release - slow
Sonic Adventure 2: 1562 owners - 10 days since release - decent