Usually that has nothing to do with gamesNew for 6.61:
System software stability during use of some features has been improved.
I can't see system 6.60 not being able to run anything released during the system 6.61 release, game wise
also noted further down the 6.61 update page is
The above may just be because they included 6.60 info thoughIf your PSP® system software version is 6.60 (or later), you do not need to perform this update. To check the version of your system software, go to Settings (Settings) > System Settings (System Settings) > [System Information]. The information is shown in the [System Software] field.
I am finding it odd that this time there is only one update file for both the PSP and PSPGo versions in the past they had seperate updates
also if anything effected Game stuff they usually mention this, for example:-
Game
Support for PSN titles has been expanded
But for update 6.61 there is nothing mentioned about Game updates
EDIT my mistake on the PSP Go update it's just further down the page