COD4 or HL2: Orange Box?

I cannot friggin decide which one to get, they both seem amazing games. Help me decide and I'll give you a cookie.

The decision comes down to this.

CoD4 strong multiplayer with a 4 hour single player campaign.

Orange Box 20 hour campaign with a decent multiplayer that has a low population.

3 games is better than 1 right?

I say the Orange box.

i dont think so, TF2 isn't a weak multiplayer, its fun and addictive.

but i suggest you rent both of them and see what you like, thats what i did