ned's blog
[SS2] How to add Ping, FPS and Map Name info to your screen. 
Most games I play I like to have my Frames-Per-Second (FPS) displayed. With Serious Sam 2 this can be done as well as other things.

Here are the additional items I have displayed and the settings needed to achieve this.
hud_bShowLevelName = 1
hud_bShowPing = 1
prf_bShowFPS = 1

// Click image to enlarge.

This display cannot be turned on/off from the ingame menu. The settings must be entered into the console (or editted in your config file). See my Serious Sam 2 FAQs for some console info - link -