it seems your previous saves were for a different region, if you use different save for example "BLES00229SGTA401" (gta 4) and your game disc has "BLUS00229SGTA401" the game won't recognise your save files as it's different region, you can change the region of your saves but you need software like xploder to do something like that.
to find out what games are incompatible just copy all your saves to a usb drive and then compare the game id to your games and then you can change the region accordingly.
PS3 Slim v3.55.4 CFW Rebug 1TB Internal, External 2TB
XBOX 1 with XBMC
Wii 3.2E + Cfg UsbLoader External 1TB
DS lite & DSiXL + Cyclo ds 8gb micro sd DStwo 16gb micro gd
PS2 V14 legit matrix infinity modchip
PSP slim 2006 5.00 M33-6 8gb memory stick pro duo
PSPgo with 16GB M2 6.60 PRO B10