Just try starting those games from a terminal.
The menu config file for fluxbox looks like this :
Code:
[submenu] (Games)
[exec] (gnibbles) {gnibbles}
[exec] (gnobots2) {gnobots2}
[exec] (gataxx) {gataxx}
..
..
The one in paranthesis is the display name on the fluxbox menu and the one in the curly brackets is the executable. So if your path is set properly, typing gnibbles in the terminal should start the game and similarly should start the game from the fluxbox menu....
The config files for fluxbox are present in
(Global) /usr/local/share/fluxbox (For me fluxbox is installed in /usr/local/bin/fluxbox)
(Local for user)~/.fluxbox/
Hope this helps