Blaster395 said:
Or you could go for free gaming with FREEWARE.
OpenTTD
Dwarf Fortress
Nethack
I won't object to Dwarf Fortress and Nethack, but I find Simutrans to be more interesting than OpenTTD (which is pretty unchallenging, it's still worth a look though as Simutrans can get frustrating if you play it the wrong way).
Another few games that are worth a look:
Supertux (it's Super Mario, just with a penguin and better graphics, and also without that stupid 3D).
The Battle for Wesnoth -> A turn-based (you can actually overthink what you're going to do) strategy game, set in a fantasy world. Or rather, fantasy worlds: there are literally hundreds of add-ons that add campaigns and maps and even story scenarios for Multiplayer.
Supertux kart -> Mario Kart, but free
Rigs of Rods -> if you've got a decent CPU, check this one out: a driving game with an emphasis on destruction. Unlike Flatout 2, this one has a complete soft body physics system, so parts will deform instead of falling off immediately.
Planetside 2 -> free to play and nice, this game looks great, but has steep requirements. Three factions fight each other on several gigantic continents. This is a MMOFPS and is one of a kind.
More on the subject though, I think that Fallout 3, TES IV: Oblivion, Just Cause 2 and Flatout 2 are all worth a mention, since they all offer lots of entertainment even for people on a little budget (though Flatout 2 has an admittedly "short" gameplay tiem of only 10+ hours).