Topic: how often do new games come out (is there a set day , like every monday)

or is it just random

If you're reffering to the Wii and DSi shops then yes, new games hit those services every monday at 12:00pm Eastern Time

Monday is when 99.5% of games on Nintendo's Download services (DSiWare, VC, WiiWare) come out. Flipnote Studio launched on a Wednesday, for whatever reason, and I'm pretty sure that's the only exception to this besides when the services first launched.

Also, Monday is only North America and other countries get different games.

Mondays for NA
Tuesdays for Japan and South Korea
Fridays for PAL

^ what Mickeymac said :3