While you're playing your Sims, your Sims play games, too.  But not all games Sims play are equal !

Video Games
There are a whole host of ways your Sim can play video games.  And they do seem to love them!  Your most efficient option is to buy a computer, which gives you a lot more functionality for your Simoleons.  Since a computer can not only play video games, it can also be used to check real estate, find your Sim a job, write novels, and many more options.

However, the video game console gives your Sim a boost to their Social need, if they play against another Sim.  

Chess
Chess can be played solo or with another Sim, at home or at the chess boards in the parks, and also on the computer.  Chess boosts Social need if you play with another Sim.  

Unlike any other game, chess will also build a skill - Logic.  Sims who have a high enough Logic skill can enter chess tournaments, and invite over the next ranked opponent for a game.  This is also the only game that has its own Lifetime Wish, "Chess Legend."  A child who plays a lot of chess is very likely to wish for a chess-related or logic-related Lifetime Wish.

Foosball
The pool table was one of my favorite items in Sims 1 and Sims 2.  Place a pool table in your front yard and you were pretty much set for social interactions!  In Sims 3 so far we only have a foosball table.  None of my Sims have showed much interest in this game.

Sim Gnubb
This is an outdoor activity which was introduced with the Ambitions expansion pack.  You can play it in your own yard, or pack it up and take it to a park to play there.  Sims really seem to love Sim Gnubb - it's one of those games that's an "attractive nuisance," meaning that uncontrolled Sims will often wander outside to play, and they will play it until all their moods go red.

Sim Gnubb is based on a real life lawn game called Kubb, which is popular in Sweden.  Described as "a combination of bowling and horseshoes," Kubb is exactly like Sim Gnubb, although the blocks are not shaped like Freezer Bunny.  (More's the pity!)

Tag and Catch
These are games that child Sims can play.  This is a great way to make friends, and to entertain your child Sims while getting some exercise.  Children can also play these games with adults, which is a good way to help boost the relationship between adult and child, while boosting the Social needs of both.

A child who plays a lot of catch with the football or the baseball is more likely to roll a sports-related Lifetime Wish when they grow up.

SimLife Goggles
These virtual reality goggles certainly entertain Sims… up until they scare the blue puddle right out of them.  I hardly ever have a Sim use the goggles without ending up with a negative moodlet.  They hardly seem worth the bother and expense!