If you want a game with various game modes that will (most likely) last you at least 50 hours and you don't want to pay that much for it, GMod has you covered.

+Various game modes like roleplaying, murder, TTT, surfing, prop hunt, cinema, sandbox, flood etc.
+While it's fun solo, it's even better with friends
+Steam Workshop, you can find anything from huge maps to player models from any game you can think of
+Active playerbase even though the game is +10 years old

-You should get CS:Source along with GMod if you don't want to bother downloading textures for it from some website which doesn't work half the time (for a few friends). This is so that you don't get pink checkerboards and glowing red "ERROR" signs everywhere.
-Servers with lots of mods can cause low framerates even on high-end PCs
-(Especially if you don't have some mods most servers use) Logging on a server for the first time can take some time if you have slow download speeds.

Edit: Spelling

If you want a game with various game modes that will (most likely) last you at least 50 hours and you don't want to pay that much for it, GMod has you covered. +Various game modes like roleplaying, murder, TTT, surfing, prop hunt, cinema, sandbox, flood etc. +While it's fun solo, it's even better with friends +Steam Workshop, you can find anything from huge maps to player models from any game you can think of +Active playerbase even though the game is +10 years old -You should get CS:Source along with GMod if you don't want to bother downloading textures for it from some website which doesn't work half the time (for a few friends). This is so that you don't get pink checkerboards and glowing red "ERROR" signs everywhere. -Servers with lots of mods can cause low framerates even on high-end PCs -(Especially if you don't have some mods most servers use) Logging on a server for the first time can take some time if you have slow download speeds. Edit: Spelling