I have not yet found any OS/2 game that would not run on eCS. So far everything I've tried runs fine.
As for Dos and Windows 3.1, all of that compatibility is still there, eCS still runs DOS better then DOS, Windows 3.1 better then Windows 3.1...
Hi
And DOSBox runs DOS games better than the eCS(OS/2) DOS VDM - due to the choice of "fake" soundcards so the games can make noises :-)
DOSBox for OS/2 is here
http://www.joschs-robotics.de/dosbox/Regards
Pete