The nifty thing about this is that even if you own the base game and nothing else, you get the Ultimate Collection for free. The Ultimate Collection includes all expansions and stuff packs ever released for the game, including Holiday Stuff which was a limited edition stuff pack and now goes for around $200 on Amazon due to its rarity.
So the big news recently is that Origin is giving away The Sims 2 Ultimate Collection to all Sims 2 players.
