Some games give you a new toy, some games give you a toybox, some games give you an entire fucking Toys-R-Us.
Some games give me so much value (which i define as enjoyable playing time) they spoil me for everything else. Like GTA:Vice City and the megaGTA, San Andreas. Besides 3 major cities and a whole state between, 100 storyline missions (some of which took a lot of play to win) there's a massive slate of side missions, car, plane, boat and motorcycle schools, unique jumps, races, vehicles to collect, property to buy, three main gangs to defeat, 100 hidden objects in each city, 6 girlfriends, a food/working out thing affecting your weight, lots of clothing, tatt and hair (and vehicle) customizations, and a dozen radio stations, all wrapped in a big story. Just driving around collecting weapons and messin with peds, gangs and cops is more hours of fun.
And then there's Civilization3 and 4. Choosing a civ (each w special units, bonuses & leaders) then building an empire, founding cities, building roads to resources, choosing buildings, religions, government types, building domestic and military units, developing technologies, interacting with the random AI civs, trading, researching/buying/selling tech, starting wars, deciding which of several ways to win, and then making sure the others don't get there first.
Sorry to go on like that - I assume many of you don't play these TBS games, but damn they're addictive. And fully customizable: 7 difficulty levels, 5 sizes of random maps, climate, numbers and attitudes of AI, plus variable barbarians, mean massive replay combinations, but you can also design your own units, maps, civs, and change all unit stats, and there's a thriving mod community, and multiplayer.
I'd say I spent a year of my life with each of these. And yes, for some of them I had to upgrade my pc, but totally worth it.