third entry, thanks!

Already got this game but... Worms?

Stronghold

age of empires?
counterstrike against bots? played it on lan but dont know if it is possible online?
dungeon siege was great only minus is its only for 4 people -_-
stronghold crusader

5 pax normally is RTS, FPS, Sandbox Multiplayer.

A good bonding 4 pax will be Move or Die on my recommendation =)

Thanks for giveaway:)
You could try some GTA V, CS:GO or L4D 2