Any PS1 - PS2 like controller should work, since they have a d-pad and the usual buttons.
#EDIT: Yes, for DS a controller won't help for the Stylus part. XD
I do remember from the ePSXe board some input problems with those that used converters/adapters. Might be just a few that gives problems or something.
Anyhow, long ago I bought an El-Cheapo USB Dual-Shock controller for $10 that works perfectly (except rumble outside of WindowsXP) for PSX for example, since it has "full range" for the analogs.