1. check if the game is reported as working on compatibility lists.
2. if set as working, check if there's a specific setting or version of DM/DML to use for that game.
Two main compatibility lists:
official, from Crediar :
http://crediar.no-ip.com/gc/
Wikitemp, from all users:
http://wiki.gbatemp.net/wiki/DIOS_MIOS_Compatibility_List
Like you can see, all 3 PAL "Tom Clancy's Splinter Cell" games are reported as not working on Wikitemp. It's probably a problematic game, not your setting.
The NTSC version (on Crediar's list) of Chaos Theory is RED, which means it doesn't work.
The other Splinter cells are marked as compatible with DM2.2 (users probably didn't test/updated with later version, it doesn't mean it won't work), but you need a disc in the drive, and disable NMM.
Always try the games in "Raw" mode in DMToolbox, if it works then you can try to use compressed, DiscEx or GCReEx if you want, but it's not required.