did a little number-crunching on the Xbox Live Arcade leaderboards for last month, and while we don't have exact numbers on Xbox Live titles (other than Major Nelson's usual list of most-played and purchased games), these are usually a rough indication of what business was like on Microsoft's network last month.
Bionic Commando: Re-armed 2 was the biggest disappointment, picking up fewer than 10,000 players on the leaderboards, compared to over 130K first-week sales for the first title. Hard Corps: Uprising, the first game to come out under Microsoft's "House Party" banner, brought in a few more players, at around 27K, and Bejeweled Blitz Live did pretty well (for a game that's on nearly every platform known to man in its basic form) with over 14K new players in the single week of February it was out.
Sales were big drivers -- Hydrophobia picked up over 10,000 new players thanks to a sale, and Geometry Wars 2 saw a huge bump as well. Outside of the new titles, Pinball FX 2 and Trials HD continue to grow their leaderboards.