Not a long game, but fun one I posted a little while ago: Link
World of Goo is a strategy game based on building structures from goo balls.
For an older game, X-COM2 is fun, hard and can take a long time to complete, though you may need something like DOS Box to play on a newer OS.
666 kilometers away from Earth there is a very small planet called Atom which is inhabited by various microorganisms. They tolerated Earth for centuries, but the stink that was coming from it became unbearable. They decided to launch an invasion. By infecting domestic and wild animals Earth would be conquered. Alas their evil plan was stalled by the scientists who are developing antibodies that will nullify the infection and put their invasion to rest. Now infected animals are going from laboratory to laboratory in which scientists hide in order to destroy the research. Scientists hired mercenaries from security agency "Protector" to protect them from pesky microorganisms. Professor Klang discovered that the micros are attacking a nearby laboratory hidden on a farm in the USA. It is up to Jack, the leader of Protector, to set up the defenses and lay waste to the little evil doers.
LOL the Story its cool, i download it now on Mega Upload^^
If you are into point and click adventure games. I would recommend Syberia and Syberia 2 They are close to a decade old now but I just recently bought them from Steam and I am enjoying them. What types of games and genres are you into?